Tire and wheel sizes for a ’93 325is at the track?

[JonW]

I’m trying to decide on tire and wheel sizes for my new ’93 325is that I got mostly for track duty. I may well end up turning the car into a racer, so I want to keep things stock legal for BMW club racing and SCCA racing. I’ve done searches, but can’t find the answers to these seemingly simple questions.

-What was the stock wheel and tire size for the car? Mine does not have the sport package. I think the stock wheels were 16”.

-What would be the optimal wheel and tire sizes to go for, performance-wise, that will still be stock legal? BMW CCA rules state that you can go 1 inch wider and 1 inch bigger in WHEEL diameter than what the car came with. But I don’t know what the car came with or if going too big would just weigh things down and hurt performance. I can’t find the SCCA rules online anywhere. And what about TIRE size?

-What are the widest tires that the car can take without problems?

I’ve got a set of BBS RK wheels with SO3 tires on them (235/40-17) from my E46- great street combo for the track. I’d like to put them on the E36, but I’m not 100% sure they will fit or that they would be legal. Maybe I’ll just use that for a while, until the SO3’s wear out. But I want to start getting used to whatever I might be racing with (e.g., if I have to go to skinnier tires). I’m perfectly happy with the RK’s, though, so it would be nice to just use those.

Thanks.

[Pinecone]

I?m trying to decide on tire and wheel sizes for my new ?93 325is that I got mostly for track duty. I may well end up turning the car into a racer, so I want to keep things stock legal for BMW club racing and SCCA racing. I?ve done searches, but can?t find the answers to these seemingly simple questions.

-What was the stock wheel and tire size for the car? Mine does not have the sport package. I think the stock wheels were 16?.

-What would be the optimal wheel and tire sizes to go for, performance-wise, that will still be stock legal? BMW CCA rules state that you can go 1 inch wider and 1 inch bigger in WHEEL diameter than what the car came with. But I don?t know what the car came with or if going too big would just weigh things down and hurt performance. I can?t find the SCCA rules online anywhere. And what about TIRE size?

-What are the widest tires that the car can take without problems?

I?ve got a set of BBS RK wheels with SO3 tires on them (235/40-17) from my E46- great street combo for the track. I?d like to put them on the E36, but I?m not 100% sure they will fit or that they would be legal. Maybe I?ll just use that for a while, until the SO3?s wear out. But I want to start getting used to whatever I might be racing with (e.g., if I have to go to skinnier tires). I?m perfectly happy with the RK?s, though, so it would be nice to just use those.

Thanks.

I can't help you on the original sizes, but once you find them, you should be able to go +1" all arond on the larger wheels available from the factory on the car, standard or sports package.

But you don't want to go larger than 17" anyway, if nothing else, the tire selection goes down ad the price goes UP.

SCCA rules are only available for Club Racing by buying them from the SCCA. The AutoX rules are online, but only because somebody took the trouble to do so. But for ITS racing, you might want to call BimmerWorld as they are THE people to built BMW ITS cars.

[JonW]

Hi Terry,

Thanks for the info. I spoke with TCKline and Bimmerworld yesterday. Sounds like 15x7 is the wheel size I need for SCCA ITS. BMW club racing is more flexible. Might as well go with the more restrictive rules (in this case ITS, normally BMW stock is more restrictive).

Maybe once my SO3's wear out, I'll go straight to the 15x7 wheels. The cost of the new wheels will be partly minimized by the cheaper tires, as I go through more sets.

[Pinecone]

If you want to run both series, prep to SCCA ITS rules. ITS legal cars run Prepared in BMW CCA Club Racing. BMW CCA preped cars may only run in something like ITE where you will be running against Vipers. :)

[JonW]

If you want to run both series, prep to SCCA ITS rules. ITS legal cars run Prepared in BMW CCA Club Racing. BMW CCA preped cars may only run in something like ITE where you will be running against Vipers. :)

Are you implying that the 189 German horses of my 325 can't take a Viper down the straight? :p

What you said is what I understand. I'm not concerned about being competitive just yet. Only to get out and experience racing. So preping for BMW CCA stock will be a cheaper place to start. Although I'm not even that far along. Got the car, tightening it up now. Maybe another season or two of driver schools and try a few racing schools. And then go for the full cage, seats, harnesses, etc. Sounds like fun to me. :angel:

[Pinecone]

Are you implying that the 189 German horses of my 325 can't take a Viper down the straight? :p

What you said is what I understand. I'm not concerned about being competitive just yet. Only to get out and experience racing. So preping for BMW CCA stock will be a cheaper place to start. Although I'm not even that far along. Got the car, tightening it up now. Maybe another season or two of driver schools and try a few racing schools. And then go for the full cage, seats, harnesses, etc. Sounds like fun to me. :angel:

I would say though, get the SCCA rule book, and don't do anything that will have to be undone for IT rules. And beofre going to BMW CCA Prepared rules, I would build towards ITS, just more options on racing.

[scottn2retro]

I would say though, get the SCCA rule book, and don't do anything that will have to be undone for IT rules. And beofre going to BMW CCA Prepared rules, I would build towards ITS, just more options on racing.

Jon, congrats on getting a track car! :bigpimp:

The main reason for the recommendation above is that BMW CCA rules have provisions for allowing crossover cars from SCCA and classes them appropriately. So if you want to run in multiple orgainzations and SCCA is one of them, build to the SCCA specs. :)

[JonW]

Thanks guys. Sounds like a good plan. I'll have to pick up one of those SCCA rule books soon. Sounds like SCCA just has more opportunities to go to the track.

I don't officially have my track car in my possession yet. I paid for it and it's waiting for me to pick it up. It has to wait a few more weeks when I can get away from work (I have to work to pay for my downward spiraling track habit :bigpimp: ). I will post all the details in the Track forum once the car is in my garage. But a quick preview is that it's a regular '93 325is and I will gradually build it up. Just for driving schools this coming season and maybe next. I'm now ordering parts to tighten it all up so that nothing rips apart. I need to find someone local to teach me how to do some of the regular mechanical repairs the car needs (timing chain tensioner, knock sensors, some belts, etc.) I dropped some $$ yesterday at TCKline. Ordered mono-ball/spherical rear trailing arm bushings and rear shock mounts. I'll order new brake rotors, pads, an X-brace, harnesses, etc. soon. This is going to be very fun. :D

[scottn2retro]

Thanks guys. Sounds like a good plan. I'll have to pick up one of those SCCA rule books soon. Sounds like SCCA just has more opportunities to go to the track.



You can get the SCCA GCR from Pegasus Racing Supply (in Wisc.) and cheaper than from the place listed on the SCCA site :D

Did you see the GTS challenge thread in the Motorsport forum?

[JonW]

Scott- Thanks for the tip on the rule book.

Yup, I saw the thread on the GTS Challenge. Sounds great- there are some races near me, in Indiana and Ohio. But I'm not ready for that just yet. Got to spend a season getting the car in track ready shape and get me to be a much, much better driver than I am now. Some racing schools, too. And then I'll add the cage, seats, etc. to make it a race car for such events. It does sound fun.

How's the M3 these days?

[scottn2retro]

Scott- Thanks for the tip on the rule book.

Yup, I saw the thread on the GTS Challenge. Sounds great- there are some races near me, in Indiana and Ohio. But I'm not ready for that just yet. Got to spend a season getting the car in track ready shape and get me to be a much, much better driver than I am now. Some racing schools, too. And then I'll add the cage, seats, etc. to make it a race car for such events. It does sound fun.

How's the M3 these days?

If you get a chance to go watch some of those races, it's a great place to pick up good info.

I have to firm up a couple of things, but I should soon be able to make some announcement on what we'll be up to this year (some nice surprises :eeps: )

[JonW]

Excellent- good luck with that.:thumbup:

I'm slightly jeaous that you can go to the track year 'round- still snow on the ground here. But I've got some work to do on the car before I can bring it to the track anyways. The season here should start by then.