Anti-roll bars

[Murph7355]

So as part of my recommissioning journey I've bought some new wheels. They're wider than the current ones (8in versus 6in), but unfortunately these are fouling on the anti-roll bar drop link.

My car's a '95 chassis and the ARB is overslung, picking up on the top of the deDion tube rather than a dedicated bracket on the deDion ears as I think newer cars do.

It looks like I might be able to relocate the drop links to the rear side of the ARB/inside of the deDion pick up. Which I think *might* give just enough clearance to the wider wheels (which I want to use ).

Has anyone done this before and know if this is possible?

The other options I see are:

- remove the ARB completely. Some reading I've done suggests this might be preferable for mainly road use....but then I like the way the car handles I believe removing the rear ARB will make the rear softer which will induce understeer (undesirable!)

- get an underslung ARB and make modifications to fit as per a modern chassis/set up - likely to be a lot of faff

Does anyone have any advice?

[BertBert]

I can't help with how to make the arb work, but regarding the handling, if you have gone from 6" rears to 8" rears, you'll get more rear grip (#obvs) and I'd expect that if you don't run a rear arb, you may well end up in understeer city. It's easy to try though of course!

Just out of interest, what has made you change?

Bert

[Aeroscreens]

'93 chassis with overslung rear ARB - When I fitted 8 1/2" Compomotives to the rear for sprinting I did exactly as you suggested by moving the ball joints to the inside of the ARB and De Dion and this works but even with fitting half-nuts on the ball joints I found the 235 profile tyres were rubbing on the ball joint nuts. Subsequently I removed the ARB and suffered a lot more understeer even with 7" fronts

I then decided to retrofit an underslung ARB and made the trip to Arch one Saturday morning and they drilled and fitted 2 bosses each side on the lower rear chassis rails .

I then purchased a 2nd hand ARB (overslung and underslung are 2 different lengths), hex spacers and re-used the mounting brackets.

You might also find the the inner rims of the wheels foul on the de dion ears so grinding off a few mm will do the trick.

[Murph7355]

BertBert said:

I can't help with how to make the arb work, but regarding the handling, if you have gone from 6" rears to 8" rears, you'll get more rear grip (#obvs) and I'd expect that if you don't run a rear arb, you may well end up in understeer city. It's easy to try though of course!

Just out of interest, what has made you change?

Bert

A couple of factors.

- I want to get my MB mags (6in width all round) crack tested so therefore needed to source another set of wheels. Ones of equivalent weight (eg Force Racing) were very expensive, and a set of R500 8 spokes came up. Not as light, but not bad. And they look good. They are also half the price of a set matching the MB weights. The rears, however, are 8in.

- tyre choice. From some research it sounds like Avon ZZS are pretty much the pick at the moment. CR500s that I last had on the car aren't available now (I believe). Yoko A021Rs are, and tbh were my favourite road tyres (the car hasn't been used for an age while we had a young family - my boys, 5 and 8, are now both showing a keen interest in the cars that were mothballed so away we go ) ...but tyre tech moves on so am thinking they may no longer be? If the MB wheels check out I may yet go the Yoko route. (Other options are to get some slicks for track days - though the chances of having spare time for that in the next few years are slim - or to sell them on)

Anyway...the ZZS only comes in a 215 width (185 being too narrow and 245 being too wide) and squeezing that onto a 6in rim would be a stretch IMO. The car currently has 205s on the rear so the amount of rubber on the back won't be changing that much. So I'm not expecting that in itself to create issues

(btw, whilst the weight is in the wrong place, the extra on the wheels has been saved on the battery - have gone for a Lithium one to replace my old and trusty Red Top 700. 5kg saving or thereabouts - and the RT700 was quite light at the time. Haven't tried starting the car yet mind...that will come later).

Aeroscreens said:

'93 chassis with overslung rear ARB - When I fitted 8 1/2" Compomotives to the rear for sprinting I did exactly as you suggested by moving the ball joints to the inside of the ARB and De Dion and this works but even with fitting half-nuts on the ball joints I found the 235 profile tyres were rubbing on the ball joint nuts. Subsequently I removed the ARB and suffered a lot more understeer even with 7" fronts

I then decided to retrofit an underslung ARB and made the trip to Arch one Saturday morning and they drilled and fitted 2 bosses each side on the lower rear chassis rails .

I then purchased a 2nd hand ARB (overslung and underslung are 2 different lengths), hex spacers and re-used the mounting brackets.

You might also find the the inner rims of the wheels foul on the de dion ears so grinding off a few mm will do the trick

Thank you

My wheels are 1/2" narrower and the tyres 20mm narrower so I'm hoping that might be enough to avoid tyre contact. Will have to see, but it's sounding promising. (The drop links need replacing as they're rusted up). When I test fitted the naked wheels the ball end of the drop link was only just fouling. My other slight worry is how much the ARB deflects and whether that would bring its connecting bar into play. Will see.

If not, I suspect going the route you have is the way to go. Looking at a later build guide the locating brackets for an ARB do seem to just be bolted to the lower frame. There's then a bracket that fits to the end of the deDion tube for final location?

Ref the ears, I was worried about these but they seem to clear OK, at least on the one side I checked! I was ready to do some grinding...but hopefully that will prove unnecessary or you're likely to see me on here asking if anyone has second hand ears and a deDion tube

[upsidedownmark]

Murph7355 said:

Anyway...the ZZS only comes in a 215 width (185 being too narrow and 245 being too wide) and squeezing that onto a 6in rim would be a stretch IMO. The car currently has 205s on the rear so the amount of rubber on the back won't be changing that much. So I'm not expecting that in itself to create issues

The factory fitment on a large percentage of cars is 6" all round with 185's at both ends - just in case you weren't aware. Only higher powered cars get 8" rears and 215's. CR500's were 175 as standard.

You may have your own reasons for not wanting 185s - or I may have misunderstood, 185 is probably too narrow for a 6", but it's not really too narrow for the car..

[Murph7355]

upsidedownmark said:

Murph7355 said:

Anyway...the ZZS only comes in a 215 width (185 being too narrow and 245 being too wide) and squeezing that onto a 6in rim would be a stretch IMO. The car currently has 205s on the rear so the amount of rubber on the back won't be changing that much. So I'm not expecting that in itself to create issues

The factory fitment on a large percentage of cars is 6" all round with 185's at both ends - just in case you weren't aware. Only higher powered cars get 8" rears and 215's. CR500's were 175 as standard.

You may have your own reasons for not wanting 185s - or I may have misunderstood, 185 is probably too narrow for a 6", but it's not really too narrow for the car..

I've tried the car in all sorts of guises (have owned it 25yrs nearly).

It started out with 14" wheels with Michelins at a time before Michelin made good tyres. Least said best

Initial move to 13" was when the car had ~130-140bhp. 185s all round were fine.

It now has 200bhp and on track days 185 rears didn't give enough grip. So for most of my time with it I've been running 185 fronts and 205 rears. It handles beautifully with that set up. Neutral with applicable oversteer on demand (but only on demand ).

So I've been wanting to keep with something similar.

How much difference the extra 10mm on the rear will make, or the extra rim width I don't know. I'm not expecting much, but you never know. The extra ~1kg per wheel (will be able to note weight differences empirically in due course) is not ideal for sure.

Assuming the crack testing of the MB wheels goes OK, and assuming I don't get on with the wider rears/Avons, I can always revert to the old set up as have just noticed that Yokohama's old faithfuls still appear to be available (I could have sworn I had a nightmare getting any when I last looked which results in me getting CR500s).

(As an aside I recall wider wheels being a problem on a Le Sept trip I did. One of the racers on the trip offered to lend me some slicks to have fun with, but the rears didn't fit and none of us wanted to mess doing anything more than a wheel swap).

[DCL]

I wouldn't get too hung up on the sizes as published. I started measuring them and soon found that each manufacturer had a different reference point - some measure across the heal of the tread and other the complete tread pattern - for example the CR500 175 was the same as the R888 185 in terms of what made contacted the road. Even more enlightening was being informed by a specialist that the carcass size of the R888 was the same across sizes. It was simply the tread width that was changed. It's probably driven by marketing, and trying to cover as many sizes as possible for the least manufacturing cost. Kumho get up to similar tricks with their 215/235 sizes and that is why the profile often changes too (to make the sums work).

[braddo]

Are wheel spacers an option to try before needing to faff around with a new ARB and mounts etc?

Not sure how much space there would before the tyres might rub on the outer wheelarches when cornering. And I guess the wider rear track would increase rear grip (and lower the rear roll centre?). Maybe an adjustable ARB is needed

Does anyone put wheel spacers on Caterhams?