CSR ride height help (for CC Bilstein 'race' suspension)

[vertew]

Update 15-May-21 >> Caterham cars provided the following advice on ride height for CSRs with the Blistein race suspension: "The length of your CSR race dampers correlates with the parts which we have on the shelf. This is indeed shorter in comparison with a road specification spring/damper and therefore the ride height will be set lower than the standard setting of approximately 140mm front and 160mm rear. The recommended ride height for a CSR race suspension setup would be 125mm front and 125-130mm rear (0-5mm positive rake). However if you are going to be using the vehicle in a fast road application then a setting of 130mm front and 135mm rear will be perfectly acceptable."
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Update 01-May-21 >> I've edited the title to include 'race suspension' in case anyone else has this issue, vanishingly rare though it probably is.
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Hi all,

I've had the dampers on my CSR 260 reconditioned and I'm attempting to set the ride height.   I'm aiming for what seem to be the generally recommended settings: 140mm front / 155 rear / 15mm rake.

Adjusting the spring platforms, I've set the front at 140mm no issues.

But ... I've got stuck trying to set the rear ride height as I can't get it higher than about 150mm.

Raising the spring platforms further doesn't seem to increase the ride height.  At these settings, when I rest the car back on its wheels, there's little or no suspension droop/settle.  So, not surprising I can't get it any higher - the suspension is fully extended when up on stands and is hardly compressing when resting on its wheels.

Some other info: the car has caterham 'CSR Race' springs fitted front and rear.  The rear are 300lb rate.  The car is on a flat / level floor.  The pre-adjustment ride height was quite low at the back, around 137mm, so rake would have been close to zero.

So the question is, what ride height / rake should I be aiming for with a CSR 260, with 'race' springs and dampers?

• Should a CSR 260 with 'race' springs run lower than the usual 140mm/155mm heights?
• Am I measuring from the right point ... I'm using a point just in front of rear wheel arch, at the edge of the chassis rail and corner of vertical side panel.
• Something else ?

Pic - my rear ride height measurement location...

Any advice on this gratefully received - cheers!
Andrew.

[David Brown]

My CSR, I started with getting the sump clearance right as it is primarily a road car by the "rolling a coke can underneath" method. This also results in the lower wishbones and steering track rods being horizontal. My rear sits at 180mm where you are measuring it to give the correct rake. Can't help you with the platforms running out of stroke as I had no problems. Normal dampers usually have several circlip grooves that mean you can adjust the platforms. My car is a Superlight and came fitted with different dampers and I don't know whether it has different grooves or if yours are the same. 

[Shortshift]

I can't speak about race springs on a CSR but when I was setting mine up last summer (now sold and enjoying a new life 'sur le continent') I got frustrated about the lack of set-up data for these cars, compared to the S3 where data sheets are to found on every street corner.  I found that some Caterham specialists (no names, no pack drill) were oblivious to the nuances of the CSR and would assume that S3 geo was the way to go.  Err... no!

Anyway, salvation was at hand through Simon Lambert (CTO at Caterham Cars) who helped me with the details below for a CSR with standard springs.  Maybe they will help.

James

[vertew]

Hi both + thanks for the responses!

@Dave Brown - yes, I've heard same about horizontal wishbones for correct suspension articulation.  I'll check on the damper stroke and whether this is adjustable for my 'race' dampers and springs. 

@JamesB - thanks v much for that ... yes OEM info is fairly scarce on the CSR.  I've added your info to my own personal CSR wiki on onedrive!

Agh, I was pretty desperate to get my 7 back on the road this weekend with the 'sun' (remember that?) finally appearing in SE England and given quite a long period of dormancy while I did a refurb on the rear suspension and dampers.  Thought I was nearly there, just needing a tweak on the ride height, then another area of complexity opens up.  Deep breath + cup of tea.  All part of the fun.

cheers.

[adrian.britnell]

Hi Andrew

just popped out into the garage and measured mine ..... at your measure point I get 160mm (approx)

Regards Adrian

[Toughie]

#3, James,

Thanks for that, James.  I didn't have that, so I'll put it to good use ready for the next time you drive my car.

[vertew]

@Adrian - thanks, 160mm would be about right according to settings from James and general advice.  I'm 10mm less than that at the moment.  My rear tyres are nearly toast though, so can probably take off +5mm.

@Toughie / James - re. the settings info, what stood out for me is how little negative camber seems to be recommended for CSRs.  I'm running around -1.5 at the moment, which I think is not unusual for s3/sv cars.  I might try winding camber back a bit.  Of course a lot depends on how the car is being used for, balance for track / road use, etc... 

Yet to find the time to have another go messing around with the spring platforms to get to a reasonable ride height ...

cheers.

[adrian.britnell]

Andrew

have you seen Steve Marsh's web site/page :-

http://www.sjmmarsh.f2s.com/

There is a lot of very useful CSR stuff on there...... including suspension details

Adrian

[MarkTheGoose]

Funny I just logged in to post a question about raising the engine in the chassis of my CSR, to stop the sump hitting the ground quite so often, which I'll do in a new post.

A couple of weeks ago, I went down the route of getting all my suspension aligned correctly on a Hunter. My ride height is right at the top end of the settings that James provided above 147mm front, 166mm rear, however, it drops to 145 & 163 when I lower my 80kg into the driver's seat. I decided not to go any lower as I wanted to keep the 18mm rake and the lowest point of the sump is only 75mm off the ground at this ride height.

Got most of the other settings right now, mine was running 2 degrees of camber at the front and only 4 degrees of caster, now set to zero & 5.5 - couldn't get the caster any further, I now have all the washers behind the lower wishbones. I also had toe out at the rear, and it's more stable now that's gone...

[Shortshift]

"I also had toe out at the rear, and it's more stable now that's gone..."

Blimey, I bet it is!  Glad I haven't been your passenger yet!

James

[Shortshift]

"@Toughie / James - re. the settings info, what stood out for me is how little negative camber seems to be recommended for CSRs.  I'm running around -1.5 at the moment, which I think is not unusual for s3/sv cars.  I might try winding camber back a bit.  Of course a lot depends on how the car is being used for, balance for track / road use, etc"

Yes, the CSR is a different animal to the S3 or SV.  If you haven't previously seen it, the SV-R development paper by Multimatic provides some interesting insight.  There's a link to a version of it here (there are probably better links to be found, but this one seems to work):

http://fdocuments.in/document/caterham-new-susp.html

James

[vertew]

@Mark - thanks for the input, I've PM'd you for some extra reference info on your CSR, as we both share the same new damper clevis!

@James - yep I do have that paper, a very interesting read.

No news on why my rear ride height is topping out at about 150mm.  That's close to the max extension of the damper and just seems to be the eay the geometry is. 

I wonder whether the 'race' spec dampers are just shorter?  If any of you CSR owner fancy popping out to the garage, whipping off a rear wheel and measuring your damper (which should be fully extended under zero load), that would be really helpful .. and we can compare lengths (fnarr).

I'm coming to the 'it is what is' point. Think I'll just wind the spring platforms back down so that they are not over-compressed and the car still sits at 150mm.  With fresh tyres, it'll be +155mm.

cheers, Andrew.

[vertew]

There have been some more developments and I think why my car seems to have a low max ride height is pretty much resolved ... Mark sent me some pics and measurements from his CSR 260 with the road suspension (thanks v much again Mark!):

• Rear Dampers: 'Race' = ~380mm and 'Road' = ~458mm. So that's a whopping ~78mm difference in damper eye-to-eye length.
• Rear Springs: 'Road' springs are much longer and variable rate.  The springs on my 'race' dampers match the current caterham part (here) and are 7" long and 300lb.

The part I've not resolved is what the ride height and rake should now be, for a CSR with the race bilsteins/springs.

The rear ride height is constrained by the max extension of the damper strut and if set to close to 150mm, that requires spring platforms to be wound up to the extent that there's no droop, with the car sits back on it's wheels.  This would be a recipe for jumping / skipping rear wheels.

For now, I've set front ride height at 135mm and rear at 140mm (equal across the rear, with driver weight in driver seat).  This is close to what it was when I bought it.  This seems pretty low compared to the usual CSR setup advice, but that's how mine has always been, so I'm quite used to it.

In terms of how it actually handles with these springs / dampers - I can't really be objective as I've not driven other CSRs and it's a long time since I had my previous SV.  With that in mind, I'd say it pretty much feels how I'd expect a track caterham to feel.  Very little roll, pitch or dive.  On smoother roads it feels very well planted, though you can still knock the back out with the power.  On bad roads, it's actually not too bad and doesn't get deflected or thrown off line, but blimey, I need to make sure nothing can fly out of the car ...  

So, I've learned a bit more than I expected through this rear suspension / damper refurb journey.  I had no idea my CSR had the race suspension.  I'd always thought my CSR was pretty firm and I didn't particularly connect with the 'floating over the bumps' experience that road CSRs are famed for.  I'll now try to find out more about what the suspension settings should be and I'm also now really curious to find out what a CSR with the road suspension is like, which is what I thought I had!

I'll contact CC and see if anyone remembers whether there was a recommended setup.  I'll also try Luke and Team Leos + Simon at Meteor may know.

As always ... advice very welcome !

cheers, Andrew.

[vertew]

For info - I got a very helpful reply back from Caterham, which settles the question of ride height for the CSR with bilstein race  suspension ...

The length of your CSR race dampers correlates with the parts which we have on the shelf. This is indeed shorter in comparison with a road specification spring/damper and therefore the ride height will be set lower than the standard setting of approximately 140mm front and 160mm rear. The recommended ride height for a CSR race suspension setup would be 125mm front and 125-130mm rear (0-5mm positive rake). However if you are going to be using the vehicle in a fast road application then a setting of 130mm front and 135mm rear will be perfectly acceptable.

I've now set ride height to 130mm front and 135mm rear.

[Shortshift]

That's really useful information - thanks for sharing, too.

Interesting to see that the CSR in race spec takes less rake (0-5mm) than the road-spec CSR (around 18mm if I recall correctly) and a S3 car (where I think 15mm is the figure usually recommended).

James

[vertew]

Hi James ... yes, I did try mine with the suspension set up with higher rake, when I was trying to get closer to the road height settings.  It was noticeably more oversteery and not in a good way.  It's much happier with 5mm rake.

I've asked CC if they can dig out a geometry setup sheet for the blistein race suspension and if that turns up I'll post the info.

cheers, Andrew.

 

[Shortshift]

 

James

[vertew]

Got one more helpful message from Caterham ... they haven't located a specific geometry setup sheet for the CSR race suspension, but advise that "the CSR race cars run a recommended 2.5 degrees of negative camber both front and rear".

My CSR is running with all the rear camber shims installed (as it was when I got it), which adds up to -2.5 deg (though I'm measuring more like -2.2).  As the car has always been like this, hard to comment on the effect, though there's certainly no shortage of rear grip and no uneven rear tyre wear.  Front is -1.5.  I might check out front tyre wear and experiment with a bit more -ve camber ... while not forgetting that the the car is still a road car!

[Shortshift]

More useful info, Andrew - thanks (I'm still strangely interested in this, despite having sold my CSR at the end of last year.  Maybe its because I'm harbouring some guilty secret thoughts about having another one some day - or maybe even twisting Caterham's arm to supply me a CSR 'glider' for me to build up...).

Anyway, seeing that you are effectively running a full race geo on the road, what's it like given the appalling conditions of many of this country's roads?  Is it darty, does it tend to tramline, does it jink and pull-around (bump steer) over bumps and surface imperfections?

And the obvious question - given the set up, will you try it on a trackday at some point?  Should be super-fun!

James

 

[vertew]

Hi James, sorry didn't spot your message.

In terms of what it's like on an average b-road.  Difficult to be objective about other 7's as I've only driven my own CSR and a few others before that, including my own previous Roadsport (effectively an R300), but here's a view ...

Think it's best described as 'very firm, but not crashy'.  You feel the road surface very clearly, but the car does not seem to get twitchy, get deflected or thrown about.

I was always a bit perplexed by the Autocar review of the CSR from 2005, where they said it 'levitates' over the road surface ... mine doesn't really do that.  It's at its worst on a bad road with high frequency ripples.  I don't often experience this, but there's one of these in the run up to Dunstable Downs in Herts.  I don't avoid the road, but it's quite good a frothing the milk, if I've got shopping in the car .

I've always avoided single track roads as they're simply not much fun due to risk of oncoming traffic, but if I do get on one, with that is badly worn with a high crown, the CSR tends to get underside scraped.  Generally though, the car never grounds out and speed bumps aren't too bad either.

On reasonable b-roads (and better), it feels how I'd expect a track car to feel: pretty much nailed to the road with no noticeable body roll, or pitching on acceleration/braking.

Living around St Albans, a decent quantity of b-roads (in any condition) require a 20 mile drive up into the Chilterns.  My driving time is mostly spent early morning on local a-roads as that what's nearby.  By happy coincidence this suits my CSR well.  There are a some motorway junctions, away from housing, that have a few roundabouts that join up into what might be described as a 'mini circuit' .  This is the CSR's natural habitat and it feels absolutely epic here ... essentially a large go-kart with a cosworth engine.

All this is quite ironic as I bought the CSR to replace my Roadsport (R300 spec) as I fancied the more sophisticated suspension and some of that 'levitation' autocar mentioned - ref link to 2013 thread on this.  As it turns out, the CSR I've got didn't deliver quite what I expected, but I still really like it and don't don't have any plans to change.  The only thing that might tempt me is the active suspension that I think Hanns Per is trying out.  Perhaps best of both worlds?

Final points ... I've taken the CSR to Brands Hatch (Indy) and yes it was fantastic.  Brilliant track for 7s generally with the small size and elevation changes.  I had to keep speed down a bit due to noise issues.  I gradually wound it up over the session to see how loud I could go and eventually got black flagged just before the end.  I've since added some more bonnet sound proofing.  I'll def be back to Brands though. 

(from around 5 mins ... nothing much exciting to see though).

Your CSR glider idea sounds great! ... you could build up the drivetrain to your own spec.  Or perhaps just ask from a CSR with 620 drivetrain?  what a toy that would be ... .. .. ! 

Cheers, Andrew.