I am interested to know more about the wheels and tyres used on GP Bugattis, both in period and in modern times. I have seen somewhere an article about the different varieties of wheels, that partly aroused my curiosity and partly salved it, but I do not recall where it was (Bugatti Trust Newsletter?) and I cannot find it to look at it again.

From a beginner's perspective, I would like to understand the different wheel types used on T35, T37, T39, T51: what each type is called, what it looks like and what size it is.

Then for the tyres, I would like to know what make(s) and what size(s) would have been used in period, and were there strong commercial considerations, or were the choices about performance and reliabilty (and were the choices circuit and /or driver dependent). Does anybody have good pictures of tyres used in period?

Finally, the cars running today can be seen with everything from motorcycle tyres; out of period 5 block racing tyres (often Dunlop); to specially made replica or re-engineered vintage type tyres (eg Blockley, Excelsior, Dunlop). What are the pros and cons of the different options, what size goes with which wheel type (and potentially car type). Again, if possible, a picture is worth a thousand words.

Hopefully this subject will allow the experienced Bugattistes amongst us (historians, owners, enthusiasts) to share what they know about a subject that must have been vital to the Bugatti driving experience since the very beginning.

I apologise if this topic has been debated to death somewhere else (I had a good look round with the "search" function before I posted but did not find what I was looking for).

Vive la Marque!

OK, so I found the article in the Bugatti Trust newsletter (see below), and it partly answers my question.

I remain curious about tyres in period and the pros and cons of tyres seen on these cars today. Can anybody help put me out of my misery?

I know near to nothing about tyres, but I would like to give at least something to discuss:

I understood that cross-ply tyres are more flexible in every way, thereby causing less load on suspension and chassis, where radial tyres transfer more forces to suspension and chassis.

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Vive la Marque !!

With regard to drawing 43 CH 96 I believe that it was for a wheel to be fitted to the type 55 which required a larger tyre than the lighter type 51.

I don't think 35B/C owners can use this drawing to justify using wider tyres - production of these models had already ceased.

The reason for the article above being published stems from the use of wheels cast in Elektron magnesium alloy by a senior member of the VSCC which are said to be lighter and wider than anything fitted to a 35B in period. They have now been banned.

If the VSCC starts insisting on competitors complying with the rule book, several cars seen on the grid for the 2009 Williams Trophy race will not be allowed to take the start next year.

Hello,

Are the splines in the alluminium wheels part of the wheel , or is a piece of steel casted in ?

Udolahr

If I am not mistaken,the last new T35b sold was in 1939? surely after the date quoted.

Cast in I think you mean.No they are just machined into the aluminium wheel.The drum is fitted after by heating the wheel.

so , the splines are part of the alluminium wheel . Are this alluminium splines a problem after some time ? What kind of alloy is it , is it heat treated ? Can anybody show a drawing ?

Udolahr

The last type 35 chassis number is 4965 with engine no. 174T. The engine number indicates a 1929 or 1930 car which was driven by Chiron at Monaco in 1930. Although it was not finally disposed of by the factory until 1938 it was certainly not made that late.

With regard to the brake drums (either cast or pressed) fitted to Grand Prix Bugatti alloy wheels these were NOT cast in situ but either shrunk in and finally ground after fitment, or bolted on.

As I said in fact.

It is surprising just how resiliant these aluminium splines are.There are still many original aluminium wheels fitted to GP Bugattis even after 80 years.The main problem is cracking of the "spokes" But I have even seen these welded up on some cars !! certainly not something I would recommend.Personally I would never use old wheels fopr racing.I have the drawings but they are too big for my little copier.You must join the BOC or the trust and get them to supply drawings.

I am a little surprised about this alluminium splines . What kind of alloy is it ?

HEAR, HEAR!!!
That might encourage proper Molsheim Bugattis to participate!
Bugwrench

I do not suppose that Bugatti had anything better than LM25 T available in the 1920's However I am sure that there are better alloys to be found today.When I was making these wheels LM25 T is what I used.

LM 25 t , cast in sand , tensile about 250 N/mm² after heat treatment ?