wider tyres than recomended

wider tyres than recomended

Author
Discussion

scooby151

Original Poster:

358 posts

183 months

Sunday 11th March 2012
quotequote all
I managed to borrow a set of Avon a91,(until I save up a little to buy my own ;-) ) however I am a little concerned on the size.
The front tyre is 195/530/13 on a 7 inch (recomended 8-9 inch) and the rear 250/570/13 on a 9 inch (recomended 10-11 inch). Any downfalls on operating these tyres on my rims?
thanks

doctordave

176 posts

182 months

Sunday 11th March 2012
quotequote all
borrow!!!! wish i had mates like yours

LCM

444 posts

203 months

Sunday 11th March 2012
quotequote all
scooby151 said:
I managed to borrow a set of Avon a91,(until I save up a little to buy my own ;-) ) however I am a little concerned on the size.
The front tyre is 195/530/13 on a 7 inch (recomended 8-9 inch) and the rear 250/570/13 on a 9 inch (recomended 10-11 inch). Any downfalls on operating these tyres on my rims?
thanks
1 - Squidge!

2 - if they're A91 rather than A92, they must be at least 2 years old and well past their best. So it ain't that much of a lend Dave............

scooby151

Original Poster:

358 posts

183 months

Sunday 11th March 2012
quotequote all
very true, but they are far better than the 4 year old rock hard track tyres it had on it. So any thoughts on this guys?

LCM

444 posts

203 months

Sunday 11th March 2012
quotequote all
1 - Squidge wink

2 - It's all relative, Albert.

scooby151

Original Poster:

358 posts

183 months

Sunday 11th March 2012
quotequote all
1.squidge
noun; a wet fart

verb; the act of ripping a wet fart


had to look it up, sorry for being ignorant, but sometimes I cannot understand british humour ;-)





Edited by scooby151 on Sunday 11th March 22:11

LCM

444 posts

203 months

Monday 12th March 2012
quotequote all
scooby151 said:
1.squidge
noun; a wet fart

verb; the act of ripping a wet fart


had to look it up, sorry for being ignorant, but sometimes I cannot understand british humour ;-)





Edited by scooby151 on Sunday 11th March 22:11
Nothing wrong with the tyre size (I've used that size for years on 8" & 10" or 8.5" & 10.5") it's just that your rims are a bit on the narrow side so the tyres will squidge around a bit leading to a lack of sensitivity and sub-optimal grip.

A91/A92 is very soft and doesn't react kindly to being driven hard for more than 1km or so in hot weather (especially on a Radical which tend to be quite hard on their front Avons). However, if the tyres are a couple of years old the compound probably behaves a bit more like A15 which is more robust and usually good for 2km or more even on a hot (British) day.

SportsLibre

590 posts

218 months

Monday 12th March 2012
quotequote all
LCM said:
Nothing wrong with the tyre size (I've used that size for years on 8" & 10" or 8.5" & 10.5") it's just that your rims are a bit on the narrow side so the tyres will squidge around a bit leading to a lack of sensitivity and sub-optimal grip.

A91/A92 is very soft and doesn't react kindly to being driven hard for more than 1km or so in hot weather (especially on a Radical which tend to be quite hard on their front Avons). However, if the tyres are a couple of years old the compound probably behaves a bit more like A15 which is more robust and usually good for 2km or more even on a hot (British) day.
That'll be agreement 7 then (although really a repeat of a previous one) smile
Although I still use crossplys so can't comment on how the Radials will perform in practice.

scooby151

Original Poster:

358 posts

183 months

Tuesday 13th March 2012
quotequote all
I have another question then, what sort of offset would a stock 9 inch rear rim have?
thanks

LCM

444 posts

203 months

Tuesday 13th March 2012
quotequote all
scooby151 said:
I have another question then, what sort of offset would a stock 9 inch rear rim have?
thanks
Don't ask me, I've only ever used 8/10 or 8.5/10.5!

I've got a pal with 7/9s on his Clubbie and had his wheel boxes sitting in my garage for months but have just thrown them out.............. mad

Have you thought of doing the unthinkable and contacting Peterborough? They are surprisingly helpful.

splitpin

2,740 posts

204 months

Tuesday 13th March 2012
quotequote all
scooby151 said:
I have another question then, what sort of offset would a stock 9 inch rear rim have?
thanks
From memory, with 7" front and 9" rear CXRs, ET0 & ET-10 respectively; SteveP may pop in and be able to confirm as he has ordered some new ones recently I recollect.

S26VE P

2,162 posts

248 months

Wednesday 14th March 2012
quotequote all
splitpin said:
From memory, with 7" front and 9" rear CXRs, ET0 & ET-10 respectively; SteveP may pop in and be able to confirm as he has ordered some new ones recently I recollect.
i indeed have recently ordered some CXR's. Albeit for my clubbie so unsure how it translates to a PR6,
i ordered after lots of measuring 7" front @ ET0 and 9" rears @ ET-20 (this was Comps recomendation to previously supplied) these fit perfect on mine.

If you were to go 8" & 10" the ideal offsets i found would be front ET0 and rears ET-7.

Steve

Edited by S26VE P on Thursday 15th March 10:14

splitpin

2,740 posts

204 months

Wednesday 14th March 2012
quotequote all
Did you mean ET-20 on the 9" Steve?; by my reckoning that would put the outside rim in much the same position as a 10" ET-7.

SportsLibre

590 posts

218 months

Wednesday 14th March 2012
quotequote all
scooby151 said:
I have another question then, what sort of offset would a stock 9 inch rear rim have?
thanks
Sorry, another one who has no idea as I am running an old set of solid revolutions from ebay 8" and 10" which apparently came off a racing Ford Anglia!

The fronts just fitted perfectly but for the rears I need to run spacers to get the clearance, my point being that the choice of wheels is fully open and they need not be specially designed for the Radical. I do however run some small "spatt" wheel arch extensions to cover the extra width and has to cut back the sidepods to give clearance for the 8" fronts extra arc on turning lock.

Edited by SportsLibre on Wednesday 14th March 19:29


Edited by SportsLibre on Wednesday 14th March 21:35

scooby151

Original Poster:

358 posts

183 months

Wednesday 14th March 2012
quotequote all
the reason I asked, is because I am having a problem with the left side of the rear body, it seems to be a little offset, also when I clip the body there seems to be no clearance whatsoever between the tyre and the wheelarch.The right side is fine. The spacers on the left side are fully extended and the others nearly fully retracted. Cant understand what is going on, could be the body is warped.
Even though it isnt latched, you can see how the body remains higher on the left side. The right is perfect.


splitpin

2,740 posts

204 months

Wednesday 14th March 2012
quotequote all
scooby151 said:
Cant understand what is going on, could be the body is warped.
Doubt it, probably more a factor of hand laid-up glass fibre - no two bits are ever exactly the same.

Have you tried putting on one end and fully clipping it, then the other? Try back first, then try front first; if we put the front on the Prosport first and then the back, the back was not a good fit at all, but if we put the back on first and secured it with the sidepod clips and the post pins, it fitted perfectly .... and so did the front when the rear bodywork clips were used to 'pull' the front back!

Next thing to check will be the post pins: I have seen bent ones - I think this is done by people trying to do a quick-fix on the bodywork alignment and the posts being bent over at the top simply means the body gets forced back out of line as the bodywork is lowered down on the posts onto where it actually rests. Concentrate on getting the front and rear bodywork aligned then adjust the line of the sidepods to match. Just take your time to suss out what's going/sitting wrong and you will sort it.

S26VE P

2,162 posts

248 months

Thursday 15th March 2012
quotequote all
splitpin said:
Did you mean ET-20 on the 9" Steve?; by my reckoning that would put the outside rim in much the same position as a 10" ET-7.
indeedy i did mean -20. edited above now.

Steve

double d racing

306 posts

204 months

Thursday 15th March 2012
quotequote all
Are the spacers on the "prongs" that come through the rear ( the ones you put the Trev sorry splitpin through ) ? If not could be an issue....
Is the body tight/firm against these prongs ?
Does adjusting these prongs do any good ?
Are the prongs level/equal ?

Clearly prong is a technical word....
Yours
N Umpty

scooby151

Original Poster:

358 posts

183 months

Friday 16th March 2012
quotequote all
splitpin said:
Doubt it, probably more a factor of hand laid-up glass fibre - no two bits are ever exactly the same.

Have you tried putting on one end and fully clipping it, then the other? Try back first, then try front first; if we put the front on the Prosport first and then the back, the back was not a good fit at all, but if we put the back on first and secured it with the sidepod clips and the post pins, it fitted perfectly .... and so did the front when the rear bodywork clips were used to 'pull' the front back!

Next thing to check will be the post pins: I have seen bent ones - I think this is done by people trying to do a quick-fix on the bodywork alignment and the posts being bent over at the top simply means the body gets forced back out of line as the bodywork is lowered down on the posts onto where it actually rests. Concentrate on getting the front and rear bodywork aligned then adjust the line of the sidepods to match. Just take your time to suss out what's going/sitting wrong and you will sort it.

will try this, thanks
James

LCM

444 posts

203 months

Friday 16th March 2012
quotequote all
I don't want to put alarm in your mind but I've always found that adherence to the principles of lex parsimoniae will rarely serve one ill!

What are the 2 simplest explanations for your asymmetry (I actually mean your car's asymmetry for I know not whether you are asymmetrical or not)?:
- the body isn't "square"
- the rolling chassis isn't "square"

Some string, a tape measure, notebook and pencil, a recollection of basic geometry and a friend (strictly speaking, a "friend" isn't necessary as apparently a sub "slave" will serve as well) should let you resolve this question.

Oh, and pray that it's the former and not the latter.