Wheels and Tyres

[Stratos]

What size of wheel and tyre do you use on your Stratos Replica, and how do you think the various tyre sizes affect the handling of the car?

Are very wide tyres at the back the correct way to go, or are there disadvantages from fitting these wide tyres?

I know John has already put something under the Gp4 Arches thread, but I am sure he will also contribute here.

I have been taking a lot of advice about this recently, and will post my findings shortly, but I am interested in other peoples thoughts on the matter.

[David May]

I'm so glad you started this new one since I've just starting playing with tyre sizes again having obtained my Italian number plates.
No sooner do I get myself a pair of wide 16" wheels and suddenly nobody makes a decent low profile tyre to put on them -I was going for 225/40x16 to keep the gearing low for sprints.
The car was great on a combination of 195 fronts and 215 rears
but I lost some traction going down to 205s all round.
I run 205/50x15 Colways on dry events and find the car nicely balanced (their 205s have a wider tread than many 225s.)
Am I forced to 17"s or higher tyres, and a gearbox rebuild with a low final?

Dave M

[JohnB_SPY8808053]

I'm running 215-50 VR15 fronts and 345-35 VR 15 rears. As you've probably guessed, I have wide arches.

I too am preparing my car for tarmac rally but I am going to keep running the wide rear tires. I know they're not as fast in the corners. I know they're hard to get. I know they're expensive. I know they can let go rather suddenly. Despite all this, I really like them. They look great and they're what the works teams used on tarmac so I think they add to the realism of the car.

I currently have a Guy Croft Stage II Twin-Cam. It will spin the tires in the first three gears without hesitation - I don't think a V6 will have any trouble. I am compensating for the cornering issues with a turning brake. I expect this to work rather well (when I get the car back together) but it might not be legal for your racing class. The 345's can be got from Pirelli and Avon though only in limited tread patterns. I think they'll be making them for a long time though - just think about all the older Ferraris, Lamborghinis and DeTomasos that use them.

My suggestion is to either get what's best for whtaever you plan to do most in the car, or just say to heck with it and get what you like.

You know, that was probably no help at all. :D

John B.

[David May]

I never thought of going as wide as 345 - what rims do you put them on (width, offsets)?
As for grip, I have trouble getting the back unstuck doing racing starts in 1st gear (the clutch slips easier!) - and I'm getting around 5.0S 0->100kmh (62mph) so its not lack of power!

Dave M

[Stratos]

Originally posted by JohnB_SPY8808053
I currently have a Guy Croft Stage II Twin-Cam. It will spin the tires in the first three gears without hesitation - I don't think a V6 will have any trouble.

I am quite surprised at this - wheelspin in third? In a straight line or in cornering?


Originally posted by JohnB_SPY8808053
I am compensating for the cornering issues with a turning brake. I expect this to work rather well (when I get the car back together) but it might not be legal for your racing class.

What is this? Do you mean a traction control system linked into an ABS?

[JohnB_SPY8808053]

I was specifically thinking of breaking the tires loose to induce oversteer while cornering in practice. My tires are Pirelli P7's and the area where I practice driving has a rough concrete surface. I have also spun the tires from time to time by _accidentally_ using a few too many revs when starting from a light. I don't remember ever trying that in 3rd gear though.

On a somewhat related and fairly amusing note - when I got my car, there was a problem with the gear selector linkage that was preventing it from selecting what I thought was 5th gear. When I fixed the problem, it turned out that I had actually been missing 1st.

As for the turning brake, they are nothing as fancy as that. Essentially it's just a hydraulic device plumbed into the rear brakes on the car that will let you slectively lock up either rear tire. I have been told that using one takes handbrake turns to a whole new level.

John B.


PS - The rear rims are 15x12. Not sure of the offset- I'll try to measure it if I get some car time this weekend.

[JohnB_SPY8808053]

Here's the best pic of the rear tires I've got handy. I'm certainly not trying to talk anybody into anything - they are hard to find and expensive and less predictable, etc. I just really like the way they look. ;)

John B.

[Stratos]

Originally posted by JohnB_SPY8808053
I was specifically thinking of breaking the tires loose to induce oversteer while cornering in practice. My tires are Pirelli P7's and the area where I practice driving has a rough concrete surface. I have also spun the tires from time to time by _accidentally_ using a few too many revs when starting from a light. I don't remember ever trying that in 3rd gear though.

PS - The rear rims are 15x12. Not sure of the offset- I'll try to measure it if I get some car time this weekend.


Does this only happen on the rough section or can you push the tail out on a smooth corner?

Wish I had my own test track!!


Have to admit the wide tyres, and Gp4 arches, make the car look the business!!!

[Stratos]

Originally posted by David May
I'm so glad you started this new one since I've just starting playing with tyre sizes again having obtained my Italian number plates.
No sooner do I get myself a pair of wide 16" wheels and suddenly nobody makes a decent low profile tyre to put on them -I was going for 225/40x16 to keep the gearing low for sprints.
The car was great on a combination of 195 fronts and 215 rears
but I lost some traction going down to 205s all round.
I run 205/50x15 Colways on dry events and find the car nicely balanced (their 205s have a wider tread than many 225s.)
Am I forced to 17"s or higher tyres, and a gearbox rebuild with a low final?

Dave M

David,

Kumho do a 225/50x16, but not a 45.

http://www.kumhomotorsports.com/products/index.htm

[Stratos]

Originally posted by David May
No sooner do I get myself a pair of wide 16" wheels and suddenly nobody makes a decent low profile tyre to put on them -I was going for 225/40x16 to keep the gearing low for sprints.
The car was great on a combination of 195 fronts and 215 rears
but I lost some traction going down to 205s all round.
Dave M

David,

Do you have any clearance problems on the front end running 16inch wheels?

[David May]

I'm now using 204/45x16 on the front (on 6.5" Image rims) and they are about 8% lower than the original Stratos tyres.
They actually look a bit small in the arches (compared to the previous 195/50x16s) and have masses of clearance.
The latest Carson high-ratio steering rack is a bit limited on lock so I never get anywhere near to suspension contact.
There is loads of room for much bigger discs (if I didn't use 15" rims on the track sometimes) but recently the range of tyres sizes available in 16" is getting a bit limited and I would have a better choice if went back to /50 profile 15".


Dave M

[Stratos]

Originally posted by David May
I'm now using 204/45x16 on the front (on 6.5" Image rims) and they are about 8% lower than the original Stratos tyres.
They actually look a bit small in the arches (compared to the previous 195/50x16s) and have masses of clearance.
The latest Carson high-ratio steering rack is a bit limited on lock so I never get anywhere near to suspension contact.
There is loads of room for much bigger discs (if I didn't use 15" rims on the track sometimes) but recently the range of tyres sizes available in 16" is getting a bit limited and I would have a better choice if went back to /50 profile 15".


Dave M

I have been running 205/55x15 Maxsport RB5 all round on my car, with their soft compound on the front, and their hard compund on the rear. Maxsport don't do anything wider than 205.

It is now becoming almost impossible to obtain Maxsport tyres, so I'm going to have to change, and thererfore I have been talking to quite a few people about options and what would suit the car for competition use. This has included competition tyre suppliers, manufacturers, and other competitors.

I have spent quite a bit of time looking around the service areas on various events, at what similar cars are running. This has included Darrians, Metro 6R4, GTM, and anything else with a rear-mounted engine.

The Darrians are probably the closest in layout to a Stratos, and the ones I have been looking at are capable of beating the Metro 6R4s, Subaru Impreza, Escort Cosworths, etc (at least in the dry). The Darrians are all running either 185 or 205 fronts, and 225 rears, with very soft compunds on the front and medium hard compounds on the rear.

From all my observations, and from the recommendations given to me, I reckon the optimum setup for a Stratos is 205 on the front in a very soft compound, and 225 on the rear in either a hard or a medium/hard compound (rear depending on how much tyre wear you are willing to put up with).

So, as soon as my existing tyre stock is used up, and I can afford new tyres, I am going to be running 205/50x15 front, and 225/50x15 rear.

[David May]

So, as soon as my existing tyre stock is used up, and I can afford new tyres, I am going to be running 205/50x15 front, and 225/50x15 rear

David, I completely agree with your tyre choice. The 225/50x15 rears should be adequate for most events and even a medium/soft compound would probably not run too hot. Its a pity that the size is not so common on road cars and therefore not used by Maxsport or Colway.

Dave M