E36 Speedo Recalibration after size change?

[Bumpii]

Hi, I’ve never changed wheels sizes before and cannot seem to find a definitive answer. If I change my current 205/55r16 into 215/35r17 would I need to recalibrate the speedo on my 99 e36 323ic? No stretch btw.

I’m planning to run the style 5s that came w the e39 528i.

[shogun]

I will move it to the E36 forum

[ultimatetester]

Your current diameter is 24.9” and your new one will be 22.9”. There will be a big error.

You should stick with original wheel sizes.
225/50R16 And 225/45R17 (245 also fine). There’s 0 error between those sizes.

[jclausen]

Is it really going to make that big a difference

[pbonsalb]

People run the Style 5 regularly. They won’t fit as much rubber as wheels with the proper offset but most people who do this are into looks not performance. Just do the math or use a gear calculator or the gps on a map app like Waze to figure out tgevspeedo difference and remember it so you know your real speed. There is no easy speedo recalibration that I am aware of though some smart person might be able to figure one out.

[spyderg0d]

It wont be off by much. Think of it this way, the m3 (same car) takes stock like 235/40/17. Your size 215/35/17 is very very little difference, actually smaller than stock m3 tire size.. So.. Your Speedo will have very very little difference. I think with considering the Speedo is already 2mph under any given actual rate, the most your looking at is maybe 3 or 4mph faster at 60mph. I happen to run 245/45/18 on my pandem up front with 265/35/18 on rear and found myself only 4.5mph faster than my Speedo at 60mph compared from radar gun.

[ultimatetester]

There will be a different of roughly 10 mph between your current and new size. I didn’t compare it to stock size to see how much it differentiates between those.

[spyderg0d]

At what speed tho? It cant be just 10 mph across the board thats not how ratios work.

[ultimatetester]

At what speed tho? It cant be just 10 mph across the board thats not how ratios work.

Yeah true I calculated with 100 mph.

[spyderg0d]

You drive it like you stole it dont you?

[pbonsalb]

That’s a good cruising speed.

[ultimatetester]

You drive it like you stole it dont you?

Yeah I’m Dutch. It’s part of the culture.