Max Width of wheel on Grantura mk 2a?
Max Width of wheel on Grantura mk 2a?
Author
Discussion

Granny Fan

Original Poster:

36 posts

175 months

Tuesday 1st February 2011
quotequote all
Wondered what size of wheel width will fit under a Grantura? For road and racing, for the latter what are the regs concerning width? Like the look of the wobbbly style alloys, has anyone remade that style of wheel? Cheers for your help.

davegt6

92 posts

204 months

Tuesday 1st February 2011
quotequote all
To try and answer you question regarding racing - "what are the regs" that all depends upon what series or championship you intend to race in.

For FiA racing to Appendix K the wheel rims are specified within the homologation papers. If you are racing in a club series or championship then you would have to refer to their specific rules. If a wheel rim width is allowed within the series regs but physically won't fit in the wheelarch you would then have to refer to the regs concerning bodywork to see if you are allowed to flare the arches.

Sorry but your question is really too open to answer directly. Fundamentally you can run whatever is allowed by regulations and you can fit within those regulations.

jellison

12,803 posts

294 months

Wednesday 2nd February 2011
quotequote all
PM Fiscracer.

He is out to have the fastest fia Granny this year smile

Granny Fan

Original Poster:

36 posts

175 months

Thursday 3rd February 2011
quotequote all
Good point Davegt6, lazy question really, havn't chosen a series yet, need to come and watch a few races.
Best Regards.

jellison

12,803 posts

294 months

Thursday 3rd February 2011
quotequote all
You can get 6J's in but pure fia stuff might be 5.5J. Like Dave says check what series you want to do or get 5.5's with Period tyres and 6J with yokos!

You need to pin it down a bit more.

davegt6

92 posts

204 months

Thursday 3rd February 2011
quotequote all
The MkIII was homologated with 5J and 6J - 5.5J therefore not legal for FIA. I think the car in question though is a MkIIa and I don't have access to the FIA papers so can't comment on what is legal for FIA on that marque. Basically you need to do some research into what you want to do first. I agree with Jelly that 6J will fit a MkIII wheel arch (just and with some very careful offset calculations). However the MKIIa is a Beetle sspension car isn't it so take all this with a pinch of salt!

jellison

12,803 posts

294 months

Friday 4th February 2011
quotequote all
Beetle Suspension! Christ...........

BTW I don't have a Grantura (body started out as one though smile).

Dave what are you planning on doing this year, race wise?

Granny Fan

Original Poster:

36 posts

175 months

Friday 4th February 2011
quotequote all
Yes Beetle Suspension, sounds better if you say 'suspension similar to the Porsche 356 don't you know'. I am used to double wishbone susp, with other cars I have had, which handled well, so I think it might be a case for brown trousers with bicycle clips with this one.

Where would I find out what is FIA homolgamated on a mk2a?

jellison

12,803 posts

294 months

Friday 4th February 2011
quotequote all
Granny Fan said:
Yes Beetle Suspension, sounds better if you say 'suspension similar to the Porsche 356 don't you know'. I am used to double wishbone susp, with other cars I have had, which handled well, so I think it might be a case for brown trousers with bicycle clips with this one.

Where would I find out what is FIA homolgamated on a mk2a?
Maybe Ian Massey Cross? PM me and I'll give you his email.

My first car was a Beetle - ok but hardly cutting edge suspension (maybe when Adolf was about). 3000M next smile

Do you mean the back is those long blade type things? If so how is that in corporated into a TVR spaceframe? Or are you meaning the front?

Pic's?

thegamekeeper

2,282 posts

299 months

Friday 4th February 2011
quotequote all
Those "long blade type things" are called torsion bars. The front and rear suspension of all pre Grantura Mk3 cars was based on VW torsion bar suspension. Crude but effective in good condition but obviously has its limitations since the trailing arms are only "supported" in one place. Given the limitations imposed by this layout the maximum width of tyre is irrelevant, more what width will work with the suspension. The torsion bars in themelves are not a problem, after all a coil spring is also a torsion bar, just wound into a coil rather than a collection of laminates clamped in the middle.
Remember by going wider on wheel and tyre you are considerably increasing the weight acting on the trailing arm bush and the faster you go the more the effect. In poor condition or over stressed the car will effectively steer from both ends. Sometimes less grip is more.

Granny Fan

Original Poster:

36 posts

175 months

Saturday 5th February 2011
quotequote all
My first car was a Beetle also, 6V rust bucket, but fond memories, bought for the sum of 25 quid.
I digress, http://tvrgrantura.blogspot.com/ has pic's of torsion bar susp.
Will pm you for that email address jellison, thanks.
In your experience, What dampers do you recommend for road/race?

jellison

12,803 posts

294 months

Monday 7th February 2011
quotequote all
thegamekeeper said:
Those "long blade type things" are called torsion bars. The front and rear suspension of all pre Grantura Mk3 cars was based on VW torsion bar suspension. Crude but effective in good condition but obviously has its limitations since the trailing arms are only "supported" in one place. Given the limitations imposed by this layout the maximum width of tyre is irrelevant, more what width will work with the suspension. The torsion bars in themelves are not a problem, after all a coil spring is also a torsion bar, just wound into a coil rather than a collection of laminates clamped in the middle.
Oooh Please for give me! wink

I'll pass on recommending spings.

I was thinking of the hideous rear trailing arms on a Beetles rear (Eek).

I see the Granny 2 has Beetle front setup on the front and rear. NICE Pic BTW smile

jellison

12,803 posts

294 months

Monday 7th February 2011
quotequote all

No idea why the front end pic does not post!?

Edited by jellison on Monday 7th February 11:29

davegt6

92 posts

204 months

Thursday 10th February 2011
quotequote all
That suspension just looks scary to me! I guess it is fine in good condition on a road car though.

Jelly - not sure where I'll be racing this season but testing at Goodwood next Friday and will be at Spa SC and 6Hr events then fill in the dots inbetween!

jellison

12,803 posts

294 months

Friday 11th February 2011
quotequote all
davegt6 said:
That suspension just looks scary to me! I guess it is fine in good condition on a road car though.

Jelly - not sure where I'll be racing this season but testing at Goodwood next Friday and will be at Spa SC and 6Hr events then fill in the dots inbetween!
Reading an old MSport last knight BRM V16 had much the same front suspension as the Granny Mk2!

Is this a proper test or an invite track day - went along to one there last year about this time (passenger though) great day out - Enjoy.

See you at SPA.

Barbarossa

144 posts

235 months

Friday 18th February 2011
quotequote all
The homologation form for the 2a says 102mm (4"). It also lists aloy wheels as optional equipment!

jellison

12,803 posts

294 months

Friday 18th February 2011
quotequote all
gppd luck with that - FIA ! wink