BC BR Series Coilovers

I’ve just had the BC BR series Coilovers fitted to my car and it clearly needs to be set-up properly. I’m after what might be called a ‘fast road’ set-up and would like to get a better understanding of damper rates before taking it along and given it to someone else to sort out for me.

I have the 6kg/mm front and rear springs and have been trying to read up on what sport of damping level should be required to get the best level of comfort vs grip. I’d really rather not just keep experimenting with different settings, it’s too time consuming, costly and, frankly, it’s only maths and so should be pretty straightforward to calculate to a good starting point at the least.

As the ride height is mostly independent to the spring / damper rates, and the spring rate is fixed, I’d like to focus on the damper rates.

These coilovers have 30 clicks on both the front and rear (though it feels like 34 on the front adjuster?) – for starters, I don’t know what level of damping these correspond with, which I’m guessing is pretty fundamental!

The rears are tricky to get too and so not something I’ll be doing more than once if I can help it – do it once, do it right.

Now, given that each front corner is basically twice the weight of the rear corners, it would seem to me that the damping force would have to be a LOT more. I haven’t seen anyone going for this ratio on the ‘New make of coilovers’ thread – why is that?

At the moment, the rear dampers are set to 5 clicks from hard (so 25/30) and the fronts are set to 12 from hard (so 18/30). The tracking is so far out that it’s pretty impossible to work out how these coilovers perform because I just get rampant power on and lift off understeer (WTF is that about!?) at the moment. The new AD08Rs aren’t properly scrubbed in yet either.

One other question about these – do they permit corner weighting because this is something I know these cars really suffer from being a left hand drive design.

Any help on this would be greatly appreciated as I’m looking to get the work carried out within the next two weeks.

I thought the rear damping adjustment was at the bottom of the shock......

ISTR that its a single damping adjustment (ie not separate compression & rebound) - if so, the valving on the fronts versus the rears should already be set up to accommodate the difference in weight (ie you don't need to go twice as hard on the fronts, as it'll already be set up to be twice as hard anyway)

What you'll need to do is experiment on a favourite (and quiet...) piece of road, that has the required undulations and bumps

Set it up full soft and go for a drive - it'll wallow a bit and will tend to understeer

Then, set everything full hard and it'll bounce like Zebedee on speed and the back end will try to step out

now start to find a decent mid point setting, where the car absorbs bumps without pitching you into the scenery, but without more than once "bounce" before it settles

From experience, I'd suggest you start from the soft end of the scale, rather than the hard end, as I think you'll find your eventual settings are closer to the soft end if you're after "fast road", rather than "trackday"

I would suggest that the key attribute to aim for is the ability to hit the power fairly hard halfway round a corner and the only effect is the Quaife will pull you round, rather than tug you off-line. Also desirable is the ability to lift off part-way round a bend without the rear stepping out. A slight correction of line is OK, but you don't want to be adding opposite lock.

Finally, you need to be able to plant the throttle at any speed in any gear in a straight line and STAY in a straight line

If I can get all of this on Osravs and Toyo Proxes, you should definitely be able to achieve it on BCs and AD08s

FWIW, my "sweet spot" is about 20% from soft on the rear and 25% from soft on the front

I'm guessing that the lift off understeer is caused by the fact that you're way too hard at the rear (oooer missus...)

Some good reading and setup tips here:

http://www.bimmerhaus.com/tech/shocktuningTN.html

http://www.dtmpower.com/documents/howtosetupracecaradjustabledampers.pdf

Don't go too firm on the rear! I remember when I first had my Ledas fitted, I set the rear pretty firm for a track day at silverstone, corner one, turned in on a damp track and the car immediately went sideways

I’ve now got the damper strength set to 12 clicks from soft. I haven’t been able to adjust it over the weekend as I’ve been away but I drive it shortly on Saturday morning and it is totally un-driveable. The geometry is so far out that I’m looking forward to seeing the results (you can literally see how far both front wheels are sticking out! On that note, it’ll be going in next Saturday for a full fast road set up.

At the moment, I know the following are adjustable on these coilovers:
- Ride height
- Bound and rebound (same setting)
- Camber

The question for me is does it allow for corner weighting?

I believe with corner weighting, that the car is measured at each corner (obviously) and the height, camber and rebound is adjusted to take account the weight over each corner, so the height might be slightly different on one side to the other, along with the rebound hardness.

I seem to remember that Kevin 20vt had a big problem with them at first fitting. He reckon the car nearly sent him into a ditch.
He wrote about it on here I think on the bc coil over thread.

Edited to add that Kevin started to contribute to the thread at page 10. May be worth a read Trappy.
Hope it helps.

Jimbo, I’ve been searching through your old posts but can’t find what I’m looking for. I’m sure you once said that the Coupé should, in theory, handle better at standard ride hide than when lowered. I ask because it rubbed the rear wheel arch again and now I’m happier with the dampers set to 12/30, I’m going to increase the ride height to clear them. At least until I get the rear subframe refreshed anyway as it’s possibly something that worn that’s causing the wheel to protrude a few mill further on the right and so snag the wheel arch.

I've donme some reading and think I'll wait until I've had the suspension refreshed with poly bushes before having this done. Sounds like it'll be the icing on the cake but not something you can really do if you're going to be fiddling with it all in the near future.

Thanks Joe. I had a good read through before buying and so am aware of the problems a few people had that were later ironed out in the most part. It's really only the front end that's not up to snuff no and, before the tracking is done, I couldn't really say the coilovers are at fault.

The reason that the Coupe handles better with standard ride height is the angle of the wishbones

At standard ride height, the wishbones should be angled very slightly downwards towards the wheel hub - this is so that when the suspension is compressed, the wishbone prescribes an arc, which actually moves the hub away from the centre line of the car, and thus increases the negative camber as the suspension compresses

On a lowered car, the wishbones are parallel to the ground, or even angled upwards at the hub. This means that when the suspension compresses, the camber moves towards positive, which isn't desirable

The answer (which is fudging the issue) is to beef up the anti-roll bars, but this has the undesirable effect that uprating the front ARB promotes understeer, so the rear has to be beefed up even more

Quite simply, the Coupe suffers from being derived from the Tipo - it was never meant to be a low-riding, sharp-handling sports car.

Yep, as Nigel said above, it's the angle of the wishbone that effects the geometry. That said, the movement is so small with uprated dampers and springs that you'll be lucky to see an inch of travel so the geometry won't be changing to dramatically.

One thing I like about these coilovers is the adjustment. The height adjustment on the front is done at the hub mounting so you aren't altering the pre-load on the springs when you change the ride height.

Get the wheel alignment done and set the camber, etc, it will feel a completely different car once that's done. It will be a game of tug-o-war on the steering wheel until it's all pointing in the right direction.

Thanks Nigel / Jimbo. The car is currently sitting 10mm or so higher than it was on the Eibachs so I might go another 10mm higher for now.

Nigel, I am thinking about upgrading both ARBs at some point too. I just want to see how nervous it is with all of the planned mods finished first. First impressions of the tyres and suspension at the rear is that it feels VERY planted but we'll have to see. A refurbished rear subframe with poly bushes is also on the list if it is still a bit vagued

Jimbo, it's not so much a tug-o-war at the moment, the problem is that the car is VERY keen to steer itself. There is no self correcting what-so-ever. Instead, if it finds the slightest camber in the road, it will just veer off - makes for a very interesting drive!!

I only wanted these coilovers because the pre-load was independant of the ride height.

Time for a call to Elite then

Definitely wait until the rest of the setup is done, as I suspect you won't need both, just a rear



What camber are you running?

Sounds like a proper geo setup will work wonders - you should be able to get it so that its pointy into corners AND planted on long sweepers AND stable on straights

Thinking about it some more - do you have the symmetrical or asymmetrical top mounts?

If asymmetrical, have you got the top of the shock behind the centre line of the top mount, or ahead of it?

I'll have a look tonight; both at the top mount and the reasoning behind your question in the thread!

Anything I should be worried about?

LOL - if you have the asymmetrical top mounts AND you fitted them so that the centre of the shock was forward of the centre-line of the mount, you would have reduced caster quite significantly, which would reduce the self-centring effect of the steering

From memory (5 minutes last Wednesday) the L one has been installed on the left and the R on the right but I'll check tonight.

Logical, I guess.....

If they are "handed" I believe it means you have the asymmetrical versions, which is the version that gives you higher castor and stronger self-centring

Depends which way you're looking at the time...

I get so sick of the looks I get at work when I ask for specifics that I give up when it comes to the hobby... to my detriment mostly...



So I have the ones that give more castor if installed correctly, but less if not? I'm Rog knows what he's doing.

If it isn't self centering then the castor is not set correctly, get the top mounts pulled aft as much as possible if they are adjustable and you will feel the steering weight up immediately.

Take the ride height down to the same as the Eibachs, its perfectly safe at that height.
Once it's up on the ramps, view the wishbones from the front of the car, they should be ever so slightly angled down at the outboard point compared to the inboard, it doesn't have to be much at all, just ever so slightly, remember you don't have much travel now.

How much adjustment are in the top mounts on these?

I took a few snaps this morning on my way out of the house.

I'm thinking there may be a cock-up with the labelling on the top mounts

Firstly, you definitely have the asymmetrical mounts - you can clearly see that the opening for the shock is forward of the outer mounting, whereas on Begbie's, they are in line - see below





However, the aspect that's throwing me is that SURELY, the idea of the asymmetrical mounts was to increase the castor, not decrease it....

I think a question needs to be asked of BC as to the reasons for the two versions of top mounts - if they say the asymmetrical versions are to give more castor, then they've got the labels on the wrong side of the mounts

I wouldn't alert them to the fact there's a possible issue - just ask why some top mounts are symmetrical and some are asymmetrical

The second picture you posted seems to be incorrectly labeled too Nigel.

If that is a L/H top mount, then that too would give less castor angle.

I'd try swapping them over and see what castor angle you have, the change is steering weight should be immediately noticeable, it must be pretty light at the moment?

So it may just be that BC have labeled all of them the wrong way around?

It isn't just light Jimbo, it turns itself. There's no weight to it at all!

I'll have to have a word with Rog then as there's no way I can do this myself. I don't even have tools or a jack anymore

I have emailed BC to ask for the reason for the different types of top mount - I'll keep you posted

Good stuff, Nigel, I look forward to the response!

Note that early in the BC group buy thread, Barbz commented that the top mounts were "for a Bravo", which Jimbo (I think) agreed with as apparently, Bravo topmounts have less castor

Either way, I'd say that the current BC asymmetrical topmounts have less castor than the symmetrical version, which in turn is the same as the OE Coupe topmount

I also found a post from Kevin_20vt as follows…

Castor...

Looks like it was well know back then. I foolishly made an assumption that these were teething problems that were later resolved. Maybe I could get away with having them swapped over?

You should simply be able to swap the entire assembly from left to right, although that may cause problems with the hose connector brackets

If not, you'll need to remove the top mounts and flip the plates over (assuming the underside of the plate is the same as the top side)

I've had an answer, and suspect that a) Apex don't know Coupes well enough to comment and b) the factory has made a mistake



I don't accept this explanation, so I have replied with the following:-




I'll await their reply and post it back here, but I rather think that one of the current BC coilover customers needs to take this over from me.

Nigel,

Just a slight point to raise, Apex are the distributors for the kit. In the initial reply from James, he has forwarded on the reply from the factory which are based in Malaysia (IIRC), so there isn't much point stating about cars from the UK.

Hi Alexis

Yes, I realised that, but if they are selling kit in the UK, they should take care to ensure that its suitable for UK cars, not on a single 93 car that they happened to look at sometime last year

I know that the topmounts for 20v cars have different part numbers to 16v variants - anyone know what the difference is?

Just had another reply - they are going to refer it to the factory

Having had the geometry sorted and been away for 5 days on holiday, it's time for an update.

I took the car to Elite last Saturday and the geometry was checked - these are the BEFORE results.

Camber
Front left 0o 19'
Front right 1o 07'
Rear left -1o 16'
Rear right -0o 44'

Caster
Front left 1o 54'
Front right 1o 42'

Toe
Front left -1o 40'
Front right -2o 37'
Rear left 0o 10'
Rear right 0o 25'

Once he'd gotten over the results, I told them about the issues with Castor to date and the chap said that less castor can help with steering response. He said that they offer a 14 day free alignment if not happy and so it would make sense to get it done now anyway. If I'm not happy, I can have the top mounts switched myself and then return to have it done again. So I had the full tidy up completed, asking for 1 degree of Camber on the front.

Front left -1o 01'
Front right -1o 01'
Rear left -1o 14'
Rear right -0o 46'

Caster
Front left 1o 54'
Front right 1o 42'

Toe
Front left 0o 08'
Front right 0o 08'
Rear left 0o 11'
Rear right 0o 24'

The rear settings are a bit wobbly, but will be fixed to a fair degree when I have the rear subframe refreshed, I'm sure.

All finished, I took it for a spin and... it is transformed. It's now handling very well indeed. Straight line stability is much improved, even a fair degree of self alignment has returned at speed. But it still feels very nervous; too edgy at motorway speeds. I will be having the top mounts switched and then take it back for another alignment for the higher Castor. More stability at speed and more favourable camber in corners sounds very good.

In terms of the car's ride, I'm pleased to report that it's actually rather good at 12/30 front and rear. Very composed over rough / jiggly surfaces on the sort of roads that sat navs love. On Motorways and flat A&B roads it feels amazing, save for the nervous steering. Really stable and planted. It's on bumpy b roads where it's suffered a little. Too bouncy for my liking, but they're hardly the roads you use for spirited driving.

One other problem I have is caused by the 235 section tyres. With a fair dose of steering lock and a little speed, it rubs the inner arches at the front. I haven't been able to explore the levels of grip properly because of this but it's already far better than it ever has been before when it starts to rub. I'll have the ride height increased again to alleviate this.
Would stronger ARBs front and rear help this? I have a 22mm whiteline on the rear but I'm thinking of going 24mm on the rear and 26mm on the front.

Oh, now that the tyres are well scrubbed in, I have full grip in 1st and 2nd gear - which is nice

I struggle with toe settings in degrees - what is 0o 08' in mm (or where is it against the upper and lower limits)?

With an uprated rear ARB, I'd suggest going for a bit more toe-in to get the motorway stability

Also, play with your rear tyre pressures - I found that dropping the rear pressures tended to help the stability

Will be interesting to hear your findings with the top mounts switched for more caster - suggest you don't do much more playing around until this is sorted, as it will make quite a difference. High speed stability will be improved, as will "feel" and (hopefully) the twitchiness on turn-in will be reduced

I'd recommend you refrain from uprating ARBs at both ends unless you're going out on track - as soon as you uprate the front, you'd need 23mm or 24mm at the rear and (IMHO) its a bit much for the road

According to their machine's guidelines, the toe range for a
Fiat: Coupé: Rest of World: 2.0 Turbo: 1994-2001 is 0o 13' to 0o 04'. I don't have Excel on my home laptop so can't work it out using formulae I've found on the internet.

It's more how responsive the steering is than the car wandering around on the motorway. It's too edgy.

Like you say, I'll get the top mounts switched before playing with anything else but the ride height will have to go up too - I can't have this rubbing any longer.

Once I have degrees converted to mm, what would you recommend I get them to set it too?

I'd start at the most stable setting (full toe-in) and then work back from there

If its still turning in too rapidly and the back is feeling loose, you may have to back off the camber a bit

I spent ages trying to get the balance back on mine, before I twigged that it was a tyre mis-match, which clearly doesn't apply in your case

Before then though, try firming up the front damping a little (or softening the rear) - should help

If its still diving into corners, an ARB might be the only answer - suggest you search for a Lancia Dedra front ARB - slight upgrade on the OE 20vt

On another note, but related - keep a very close eye on your oil pressure gauge - I found that with trackday tyres on, it was easy to get enough lateral G through a roundabout to cause the oil pickup to starve - not a good idea, especially on an expensive forged build

Quick snap of the same side now they've been swapped over.



I'm off for a realignment on Saturday morning so will report on the Castor status then.

No idea if it handles any better yet as the shoreline ARB has snapped a bracket bolt and that now needsremoving but has to wait until next week.

Looks a lot better, although you might want to back off from max camber.....

I asked Rog to do that because the middle setting gave me 1o of positive camber on one side and half a degree of positive on the other side. 1o negative was 90% of the travel so I figured it's better in the short term. Clearly, BC didn't do a very good job on the top mount design with the asymmetric versions...

So I'm assuming that when facing the engine of the car, the coilovers are labeled correctly? Like mine are overe here

Yes, that's how they should be fitted for more Castor.

I wouldn't worry too much about having less static camber, if you're running more positive caster then you will get extra camber as the wheel turns. That's exactly how you want it, full tyre contact with the wheels pointing straight ahead and negative camber as the wheel turns in so the body roll and suspension compression will still have full tyre contact in the turn.
Should handle nicely.

It's funny you should say that Jimbo, because I was thinking along the same lines yesterday. More specifically, I was considering asking the chaps in the alignment shop if they could measure the camber on full lock. Is that possible?

If it was, then what sort of settings should I be looking at? If, say, 3 degrees was ideal in a corner and in a straight line that meant 1 degrees, would it still be worth backing off to 0 degrees and taking 2 degrees at full lock? As far as I know, it might increase it by a factor of two or more… In that case, you’d need some to get any increase!

I have no idea how much extra camber I’ll get, but how much at full lock is good?

It's way more complicated than just saying you'll have 3' of camber with the wheels turned Trappy.
In a corner, the outside damper will be compressed so the geometry will change from the static condition.
Just get them to measure the caster angle, if you're running a little more than standard then you'll be fine, if not then pull in some negative camber.

Go on then Jimbo, what’s “a little more than standard”?

Book would appear to say -0o13’ to -1o13’. Go for good old -1 degree?

Just got back from Elite. Settings are now the same as before but with 2o 47' of castor on the left and 2o 30' on the right.

Feels a lot more stable and surrfooted at speed but with the rear left ARB bracket not in place, I can't really push on yet.

Almost there!

Hmmm, you're still almost 1 degree of positive caster short of a standard coupe.

I've just checked one of my geometry printouts - with Osrav shocks and standard topmounts, I have 3.13 (L) and 3.37 (R) degrees of caster

Either Trappy has something fundamentally different going on with his car (wishbones?) or the BC coilovers are all wrong somewhere

PS - I'm only guessing, but with the BC top mounts on the other way, the caster must have been around 1 degree - no wonder it felt a bit weird to drive....

EDIT - just remembered that Trappy listed the caster earlier on - 1.50-ish - not sure I understand why flipping the mounts has added such a small amount

On my report I have 2,55 and 2,54 (degrees of caster) on both sides and values should be between 2 and 3 degrees according to the report.
I have aftermarket standard top mounts (febi bilstein).

EDIT : Fiat documentation says 3°30' +/-30'
I have Eibach springs -30mm. Can this explain the difference?

Yes - the amount of lowering will affect the caster - the lower you go, the more caster you will have

.

Are you sure Nigel? Camber alters with lowering due to the suspension moving in an arc which is hinged inboard to outboard, I'm not sure the caster angle adjusts with lowering?

The BC top mounts are at fault, they just haven't done their homework on them. Take a look at an OE top mount and look how much the spring mount and damper mounting is mounted to the rear of the mount, these BC have almost gone for a central mounting point, it's only ever so slightly aft if you fit them in the wrong positions (that's how poor the engineering is).

I just used the word "mount" 6 times in one sentence, is this a record?

No, I'm not 100% sure, but here's my rationale:-

Let's say that the bottom ball joint is 25mm forward of the centre of the shock top mount (both are clearly fixed points, so cannot vary)

At standard ride height, let's say there's 400mm (wild guess) between the bottom ball joint and the top mount - this creates an angle of (say) 3 degrees

Now, we shorten the distance between the bottom ball joint and the top mount (by fitting lowered suspension). The fore and aft distance (25mm) cannot change, so the angle of the line between the bottom ball joint and the top mount MUST get a little steeper, as the vertical distance has shortened.

The arc prescribed by the bottom ball joint with movement of the wishbone will make the bottom ball joint move away from, or closer to the centre line of the car (thus increasing or decreasing camber) but it cannot move the bottom ball joint fore and aft, so the arc will not affect caster

EDIT - contrived diagram to explain my thoughs



Left-hand line is the standard suspension (as viewed as though you're looking into the wheelarch with the wheel removed)

Right hand line is lowered suspension - the fore and aft distance of the top and bottom points is the same, but the height is reduced, which increases the caster angle

Ok I agree there will be some altering but the ammount is minuscule in the 20mm of lowering we are talking about, certainly much less than he camber created by lowering so probably not enough to recover the 1' of caster we are missing here.

I think those top mounts need a redesign to at least match the OE parts and add a little extra for good measure.

Are there any piccies of the Gaz "max caster" topmounts that are available as an option on their coilovers?

Edit - Gaz coilovers with Max-caster topmounts

Just look at the extra offset on the topmounts to create the additional caster - its massively different to the BC topmounts

I agree - any increase is there, but very minimal (and probably not detectable by the driver)

Unfortunately that view seems to be looking at the front to rear view of the top mount so we don't see how far back they are, but to put it into perspective, to fit the Gaz max caster top mount, you had to shave metal from the rear of the suspension mounting top mount cut out in the chassis!

I think Si (Suba) had them fitted to his coupe so could contribute to the mounting of them.

I did a little calculation, you'd have to lower the suspension approximately 6" to get a 1' shift in caster. I'm no mafs eggspurt but I think I got it right. It would sure look bad ass but you'd be going through a new exhaust every day.

Oh wait, the damper on the right has the other view, you can see the caster quite clearly.

Agreed - the centre line of the damper rod is WAY behind the centre line of the topmount on the Gaz kit

I've chased Balance Motorsport by email today to get them to chase the BC factory for an update

In the meantime, I thought I'd do some more research to see if anyone else is having issues with BC

Lancer boys aren't impressed - check out the photo part way down the page

Sadly, it appears not to be an isolated incident....

Fairly old thread though, so I guess BC have sorted the issue by now?

UPDATE - I've had a response from Balance - they have supplied me with a technical drawing of the BC topmounts and suggested that I should tell them what changes need to be made, and they will look into having some made.

I think this is a good point for me to hand this line of enquiry over to one of the BC coilover customers - I really don't want to be acting as middle-man if I can help it

Any volunteers?

DOH! - Not Balance - Apex

I thought you were interested in buying a set Nigel?

I was, but I'll wait until the issues have been addressed (or I'll bite the bullet and go for the Gaz setup)

with the Gaz kit dont you have to modify the chassis at some point like the D" kit which is what put me off.

reading the evo post has made me think twice about ordering the fronts now

Yes, you have to cut front suspension turrets

such a shame i dont want to cut mine if i can help it. Hope the issues with the BC's are solved

I wouldn't worry too much, you are just elongating the hole in the chassis for the damper mounting. If you keep the profile of the original rounded hole then it won't cause any stress or cracks.

So what would the risk be if I mount the BC kit that I've recently got? I've posted a pic with the top mounts and they are asymmetrical.

There's no risk, you may not run as much caster as a standard coupe which would give you less steer ahead if you release the steering wheel. The car may be slightly less stable with less steering feel/weight.

You can still pull the camber in from the top mounts but that's almost working back to front, you'd want less camber with the wheels straight ahead and more when the wheels turned which is where caster is king.

Would less castor cause more torque steer?

I don't believe so, although less caster makes the self-centring effect less pronounced, which means you can FEEL the torque-steer more easily

Torque steer is caused by many things, but is rooted in a difference of grip between the driven wheels (which could be tyre deflection, surface, driveshaft twisting, geometry etc)

I guess the only time caster could affect torque-steer is if the caster was different on each side

http://www.aligncraft.com/terms/terms.html#FrontCaster

Scroll down to caster, while it may not directly cause torque steer, the symptoms may be similar in extreme cases.

Confirmed then. It's definitely squirming and pulling on uneven surfaces now since fitting these coilovers.

You have about 2.5 degrees positive caster, so you shouldn't really be getting any caster-related squirming - does it happen on and off the power and on a steady throttle?

BTW, did you guys see Deltapart's review of the current BC Racing coilovers? I was looking to buy a set but now... No ducking way. https://www.facebook.com/delta.parts.3/videos/448819618633450/

I never used the softest setting on the rear (for the road/track) so no problem for me.

Hi, can you tell me how much adjustment is needed to get the ground clearance to be the same height as the original?
Is it difficult to reach later to adjust the rear shocks once they are installed?