Frame strain?

[yankeedoodoo]

I know some guys that autocross with 9 1/2 in Hoosier(Daddy) gumball slicks on their 7s and the cars are stars on course. a couple other 7 owners say stuff like, "That little frame ain't made to handle such torque twisting force and them boys are going to destroy their cars". And the racers respond, "Aahhh, those guys are afraid to get a scratch on their cars". Is there some sort of practical limit/common sense answer? Or, should I just get some new wheels with the proper offset and slap on a set of Bridgestone F1 tires? Thanks for any reponses!

[Peter Carmichael]

It will only be an issue in first gear.

[Nigel Riches]

Several years back I was thinking of changing from the 13" wheels on my 1982 Caterham to some more sexy bigger wheels and lower profile tyres, I contacted Caterham Cars and spoke with one of the engineers, he advised me that, although the 1982 frame was stronger than the Lotus pattern, the loading that super sticky tyres could transmit to the suspension pick-ups may cause problems, ie, cracked chassis, and failure big time, if your chassis is much more up to date, perhaps this situation won't be a problem, but it would probably be worth a yarn with the manufacturers, or Arch Motors, so watch out for those sticky gumballs, maybe the other fellows know more than just cubes, regards Nigel.

[stevefoster]

Arnie has cracked a chassis of course....

 

/Steve

 

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[ECR]

For a number of years I used 225 x 45 x 13 Hoosier Autocrossers for sprinting (and mighty fine they were). I aso did a lot of track work with 7 " Avon slicks (250BHP VX engine). At about 9 years old my chassis cracked around the diff mounting points and I took it to Arch motors who rebrazed and strenghtened the mountings. This lasted a further 3 to 4 years and then cracked again. The chassis has been further reinforced by Arch but common sense says that it will eventualy crack again. The diff mounting area is a known weak point in high power cars.

 

The extra performance from the car on good tyres more than repays the cost of any repairs (in my opinion).

 

There is no single answer to your question but I would suggest that if you only use the car with Hoosier type tyres 5 or so times a year it should not be a problem. In my case it was much more than that !

 

Edited by - ecr on 16 Dec 2002 13:27:07

[Anthony]

Hi Roger,

 

Whilst my diff area has not started to crack, it can only be a matter of time.

 

Arch have advised that early/mid 90's chassis have 18 guage section for the diff and the new ones are 14 guage + additional strengthening work. Hopefully that should last another 10 years.

 

Arch costs for the work are not significant, but diff/tank etc need to be out

 

Not sure of any other strengthing points required Arch did not have any other suggestions

 

Kind regards

 

Anthony

 

X-Flow-power; the real way forward

 

 

[yankeedoodoo]

Thank you for the wisdom imparted. Reckon I'll go for bigger tires,harder driving and fix whatever breaks.