Using tyre profile to change your 'gearing' ?

[banhama]

I have a Clio 182 track/race car, still with the OEM 16" wheels and using 205 16 45 tyres

I've had decent laptimes on the old Federal RSR-R tyres.
I've had not so good laptimes and shocking wet performance on the Yoko Advan NeovaAD08RS (probably the worst performance track tyre I've ever used)
Then the penny dropped! Coming from a high powered 4WD car it was imperative that all the tyres were pretty much the same.
In this car I can put grippy tyres on the front and the shitty Yokos on the back, and actually improve the handling by getting the rear to move out on corner entry.

I've just tried Zestinho Gredge soft compound on the front, rock hard Yokos on the back, and equalled my best lap times, but was hoping to go at least a few tenths quicker.

My home track is Lydden Hill, then Brands Indy.Particularly at Lydden I hit the limiter in 3rd well before I need to brake for two corners, but not early enough to change up to 4th and back down. I've tried short shifting to 4th early, but that just sucks laptime.

So I intended to go back to the Fed RSR-R, (it has been replaced by the RSR-Pro which I also didn't find so great) but they only have 205 16 50 available.

By my reckoning using a 205 50 instead of 205 45 would increase the rolling diameterby 20mm, so would that help getting to a higher speed without hitting the limiter?
Is the downside slightly impaired acceleration out of the corners?
If I only changed the fronts and left the rears 20mm 'smaller' what effect would that have? Apart from putting a weird rake on the car, which I could adjust out on the coilovers.

Cheers Andy

 

[JB21]

It'll will increase the ratio ever so slightly. Maybe 1-2 mph in 3rd. Might just be enough. Mine on 225/45/15 v 225/45/16 has a top speed difference of 3mph in 4th gear.

 

[Coops Mk1]

Use decent semi slicks too, rsr and ad08 are road tyres really, you want Dunlop direzza or nankang ar-1 really. Or original style r888 if you can find them

 

[banhama]

Use decent semi slicks too, rsr and ad08 are road tyres really, you want Dunlop direzza or nankang ar-1 really. Or original style r888 if you can find them

I would do at Brands Hatch and I really want to try the ar-1, but unfortunately Lydden is so abrasive it will destroy a softish compound in a single trackday.
I did heat cycle a pair of the Zestinhos which made them last a bit better, but they would never last a second trackday.
A pair of ar-1 on the front would be worth the sacrifice in a race though!

I used to get part-worn btcc slicks for the Impreza, but I don't think there are any race series using 16"?

Has anyone used this tarmac rally trye Maxport RB5, I was thinking of maybe trying the medium compound.

Maxsport RB5 Tarmac Rally Tyre

The Maxsport RB5 is a moulded slick rally tyre, designed for dry smooth tarmac surfaces. The tread pattern is designed to maximise the footprint of the tyre by using the highest permissible road to tyre contact area within FIA regulations. The RB5 is a fully E-Marked tyre, making it fully road...

www.demon-tweeks.com

 

[bozothenutter]

Federal RS-R has not been replaced by the RS-PRO, completely different tire!
its replacement is the RS-RR, the RS-PRO is much more road oriented (see the centre channel)
Tbh if you're that serious about laptime, bite the bullet, add a shorter 5th to the box, then fine tune with the final drive.

 

[Coops Mk1]

The rsr was never a very good semi anyway so whatever replaced it isn't really going to help. Abrasion I guess is a major issue but a harder compound original r888 would maybe be decent middle ground?

Does the race serious stipulate original tyre circumference? So can't drop to 15"?

 

[banhama]

Federal RS-R has not been replaced by the RS-PRO, completely different tire!
its replacement is the RS-RR, the RS-PRO is much more road oriented (see the centre channel)
Tbh if you're that serious about laptime, bite the bullet, add a shorter 5th to the box, then fine tune with the final drive.

So that's why I was disappointed with the RS-PRO! and why RS-R has limited sizes. I'll have a look for RS-RR

 

[Twingo 1??]

Don't use maxsports although they are grippy the side walls flex like crazy. Used them once on the rally car and never again.

 

[robzracing]

I would do at Brands Hatch and I really want to try the ar-1, but unfortunately Lydden is so abrasive it will destroy a softish compound in a single trackday.
I did heat cycle a pair of the Zestinhos which made them last a bit better, but they would never last a second trackday.
A pair of ar-1 on the front would be worth the sacrifice in a race though!

I used to get part-worn btcc slicks for the Impreza, but I don't think there are any race series using 16"?

Has anyone used this tarmac rally trye Maxport RB5, I was thinking of maybe trying the medium compound.

Maxsport RB5 Tarmac Rally Tyre

The Maxsport RB5 is a moulded slick rally tyre, designed for dry smooth tarmac surfaces. The tread pattern is designed to maximise the footprint of the tyre by using the highest permissible road to tyre contact area within FIA regulations. The RB5 is a fully E-Marked tyre, making it fully road...

www.demon-tweeks.com

You can pick up 15" slicks from the Ginetta series if you were to move to a 15" rim bujt I wouldn't recommend going to slicks without a suspension that can handle it. Chances are your springs will be way too soft on your coilovers.
Have you considered Yoko AO52s? They are an awesome all round tyre and a lot of club racers are moving over to them now.

 

[banhama]

Don't use maxsports although they are grippy the side walls flex like crazy. Used them once on the rally car and never again.

Many thanks for the information. I was a bit concerned about flex going from 45 to 50 profile as well, so I will definitely avoid them.

Sadly Federal RS-RR don't appear to be made in 16" anyway.

 

[banhama]

Does the race serious stipulate original tyre circumference? So can't drop to 15"?

No it's a fairly open series, so 15's might be a good option to give a lot more tyre choice, particularly as @robzracing says there might be an option for part worn slicks.
At 8kg/mm all round the springs are probably a bit soft, but I can easily get harder springs.

The A052 are used by quite a few of the other hatches, and would be worth it for racing, but currently mainly doing trackdays at Lydden I'd need to release some equity!

If I were to change to 15" and use 195x50R15 that brings the AR-1 into the price bracket, BUT it does deacrease the rolling diameter a bit rather than increase it! So then if I add a bit more power with throttle bodies I could change up earlier and use more gears....this is getting expensive!

 

[banhama]

Is the A052 the replacement for A048? That's what I was thinking of seeing other racers use last year.
Looks like a completely different tread pattern.

 

[robzracing]

Is the A052 the replacement for A048? That's what I was thinking of seeing other racers use last year.
Looks like a completely different tread pattern.

AO50 was the replacement for the 48. A great tyre also but not road legal.

 

[JB21]

You can pick up 15" slicks from the Ginetta series if you were to move to a 15" rim bujt I wouldn't recommend going to slicks without a suspension that can handle it. Chances are your springs will be way too soft on your coilovers.
Have you considered Yoko AO52s? They are an awesome all round tyre and a lot of club racers are moving over to them now.

Ive heard this a lot about spring rates and slicks. I'm running pretty basic coilovers in Meister R's with what are considered very soft springs 5kg front/7kg rear and was worried about how the car would perform on track using slicks. No issues what so ever, even temps across the tyres and performed really consistently. Entry to Lodge at Oulton park below at full tilt and coilovers not even set and max damping. Looks pretty flat for the rates I'm running, could be running a bit to much rear camber at -4 as the OSR tyre hasn't got full contact to the track. Maybe the ARB's, full chassis bracing and 6 point cage helped keep it flat? I don't feel the need to up spring rates anyway.

 

[robzracing]

Ive heard this a lot about spring rates and slicks. I'm running pretty basic coilovers in Meister R's with what are considered very soft springs 5kg front/7kg rear and was worried about how the car would perform on track using slicks. No issues what so ever, even temps across the tyres and performed really consistently. Entry to Lodge at Oulton park below at full tilt and coilovers not even set and max damping. Looks pretty flat for the rates I'm running, could be running a bit to much rear camber at -4 as the OSR tyre hasn't got full contact to the track. Maybe the ARB's, full chassis bracing and 6 point cage helped keep it flat? I don't feel the need to up spring rates anyway.

View attachment 1498557

As you say, with chassis bracing, cage, ARBs etc you've already got a pretty stiff car and a mid engine car is always going to have an advantage. The key to slicks is getting heat into all 4 of them evenly. Difficult if you have the nose diving at every corner and all the weight transferring to the loaded wheel all the time, especially on a FWD car.

 

[JamesBryan]

Plus the MR2 will have a completely different roll centre to a lowered Clio.

That's the main issue with Clios, you fit coilovers but then need to correct the roll centre in order to bring some of the handling back.

 

[Coops Mk1]

I upped my front spring poundage and fitted a roll correction kit, slicks work much much worse now and I need to re-geo for it...….softer springs and more roll was working perfectly before. damn the modding bug

 

[Martin_172]

Run an rstuner to give you an extra 500rpm on your 2 points where you are hitting the limiter in 3rd

 

[banhama]

Run an rstuner to give you an extra 500rpm on your 2 points where you are hitting the limiter in 3rd

Many thanks for the reply @Martin_172 , looks like I might be solving the problem with a higher final drive ratio as suggested by @bozothenutter .

Along with hitting the limiter I've broken 2 clutch covers in short succession at Lydden Hill, all the detail is in this rather long thread https://cliosport.net/threads/clutch-damage.834440/page-4#post-11982209

The two issues are obviously related, so it looks like the best all round solution.