Biggest Tyres I Can Get on Back Of E36

[Muzzie 0]

For gfs car, as above.

Old tyres were 205/60/15, want as wide and as tall as I can get to give more traction and to get the speedo better. For now I replaced them with 215/70s. I know I can get 225/55/15s on them, but can I go higher profile? Or wider than 225.

Curious for next time they need changing.

And to further that - same for front. They're not needing replaced for a while but again I'll be going bigger than 195/XX/15 that are on there now.

Cars too damn low. Factory iS suspension.

Thanks

Edited August 3, 2007 by Muzzie

[zenetti 0]

215/70's.......................!?!?!?!?!?!?! the guy at the tyre shop that fitted or recommended those needs to be shot!!! the car must drive and handle like a bucket of bolts, not to mention the 'old skool' arse in the air look!! 225/55's would be a much better tyre to go for.

the speedo would have been corect with the original tyres on.

[Muzzie 0]

215/70's.......................!?!?!?!?!?!?! the guy at the tyre shop that fitted or recommended those needs to be shot!!! the car must drive and handle like a bucket of bolts, not to mention the 'old skool' arse in the air look!! 225/55's would be a much better tyre to go for.

the speedo would have been corect with the original tyres on.

Wrong.

GPS puts it 10kph out across the whole speedo. And I've tried it in a number of other BMWs and had exactly the same result. Always 10kph wrong across the speedo. With the 215/70s speedo is now 1kph slow. Also meant the odometer was counting up too fast - originally a trip from my place to gfs was said to be 80.2km, GPS said its 76.1km, with new tyres its now 72.0km, so car should in theory hold value a bit better being that it now gains less kms for the actual distance travelled.

Car originally slid about all over the place with old tyres, now holds the road nice and tight and can be flung into corners much more agressively and with far more confidence. Not worried about any acceleration it might have lost (Sweet FA if any) becuase at the end of the day it's the gfs car and shes not gonna be racing it.

And the ass doesnt look any more in the air than it did before

[Muzzie 0]

Hey I have seen 155-80-13 light truck tyres recommended and fitted by the tyre shop to a mazda familia because "they were the best price in the size range"

Imagine a 900 kg car on 6 ply rated crossply truck tyres!!!!!!!!!!!

They'll never have to replace the tyres again on it

Shoulda added this in to post above but meh

[zenetti 0]

Hey Muzzie

I would not rely on GPS as being 100% accurate as it takes points along your journey rather than real time data. My mate and I go on cycle rides all the time and his GPS is always different to the cycle computer, and the cycle computer has been set up with correct tyre size.

Unfortunately I am not the one that is wrong here.The difference betweeen a 205/60/15 and 215/70/15 tyre is 8.8%, so if you are travelling 100km/h your speedo will be reading 92km/h. I have been in the tyre industry for over 4 years now and think I know tyre sizing. Don't be surprised if your gf gets pulled over for speeding.

The car probably slid about because the tyres were worn out, nothing to do with sizing. more tread = more grip.

For once I think 3pedals may agree with me

[bravo 35]

It would depend on the model of your GPS receiver. Some cheaper units may only give velocity based on time differential between two epochs of data (distance/time) but most decent units either measure the doppler shift of the carrier signal combined with the known velocity of the satellites contained in the broadcast ephimeris, or this PLUS a correction from the distance/time data to smooth out the noisy doppler result.

Long story short - a decent handheld GPS unit should give you velocity accurate to ±.5km/hr or better based on my understanding of the technology. I use it every day although admittedly not for velocity measurements.

[zenetti 0]

understand what you are saying, but it still measures the distance between 2 points and does not take into account any variances between those two points. You might go form A to B but you might take a curved arc rather than straight line.

anyway original thread was about tyre sizing - how about we concentrate on that

[Muzzie 0]

Hey Muzzie

I would not rely on GPS as being 100% accurate as it takes points along your journey rather than real time data. My mate and I go on cycle rides all the time and his GPS is always different to the cycle computer, and the cycle computer has been set up with correct tyre size.

Unfortunately I am not the one that is wrong here.The difference betweeen a 205/60/15 and 215/70/15 tyre is 8.8%, so if you are travelling 100km/h your speedo will be reading 92km/h. I have been in the tyre industry for over 4 years now and think I know tyre sizing. Don't be surprised if your gf gets pulled over for speeding.

The car probably slid about because the tyres were worn out, nothing to do with sizing. more tread = more grip.

For once I think 3pedals may agree with me

How you figure that??

If the speedo was reading 10kph faster than actual road speed then if I put bigger tyres on the car the speedo goes slower thus making it more accurate........ Thus, ifat 110 indicated it was doing 100 on GPS, then take off your 8.8% and you get 9.68 km, making it approx a kph wrong at 100.......... (considering GPS & Speedo dont measure in decimals you could in theory round it up and make correct at 100, but I'm not gonna nitpick on finer details)

Reason other tyres were changed was not lack of tread but lack of grip.......... Still had 4mm across the width and round full circumference.

And bravo - which GPS model would you like?

I've got a Navman N40I, A Navman NCN630I and 2x Navman CNC635I (all 4 are in car units), Theres the garmin handheld one floating around too

Anyways, I'm not here to argue and make enemies - not my thing

[zenetti 0]

How you figure that??

If the speedo was reading 10kph faster than actual road speed then if I put bigger tyres on the car the speedo goes slower thus making it more accurate........ Thus, ifat 110 indicated it was doing 100 on GPS, then take off your 8.8% and you get 9.68 km, making it approx a kph wrong at 100.......... (considering GPS & Speedo dont measure in decimals you could in theory round it up and make correct at 100, but I'm not gonna nitpick on finer details)

You are correct in your thinking but you are making a huge assumption that BMW have designed their speedos incorrectly. Why would BMW design their cars to read 10% 'slower' than they should from factory?

Just curious but have you tried the 5km odometer test on the motorway at Ramarama. Would be interesting to see the difference between that, your GPS unit(s) and your speedo. I think we can all agree that the 5km odo test would be a good base to start from.

If you have tried it across a number of BMW's with the same GPS unit - maybe it is your GPS unit that is out?

I can't believe that there would be a factory fault like this from BMW. Imagine trying to argue that in court if you got a speeding ticket! Honestly Sir, I wasn't speeding, BMW have designed their speedo's wrong

I still believe that your tyre is way too tall (55mm taller than factory) - are you positive it is a 215/70/15? This is the size that Honda CRV's use, so in essence you have put on a tyre designed for a SUV rather than a sedan (or coupe)

Anyways, I'm not here to argue and make enemies - not my thing

yeah I agree totally with the 'friends not enemies thing' - just good to have a nice 'discussion' about things.

[Muzzie 0]

How you figure that??

If the speedo was reading 10kph faster than actual road speed then if I put bigger tyres on the car the speedo goes slower thus making it more accurate........ Thus, ifat 110 indicated it was doing 100 on GPS, then take off your 8.8% and you get 9.68 km, making it approx a kph wrong at 100.......... (considering GPS & Speedo dont measure in decimals you could in theory round it up and make correct at 100, but I'm not gonna nitpick on finer details)

You are correct in your thinking but you are making a huge assumption that BMW have designed their speedos incorrectly. Why would BMW design their cars to read 10% 'slower' than they should from factory?

Just curious but have you tried the 5km odometer test on the motorway at Ramarama. Would be interesting to see the difference between that, your GPS unit(s) and your speedo. I think we can all agree that the 5km odo test would be a good base to start from.

If you have tried it across a number of BMW's with the same GPS unit - maybe it is your GPS unit that is out?

I can't believe that there would be a factory fault like this from BMW. Imagine trying to argue that in court if you got a speeding ticket! Honestly Sir, I wasn't speeding, BMW have designed their speedo's wrong

I still believe that your tyre is way too tall (55mm taller than factory) - are you positive it is a 215/70/15? This is the size that Honda CRV's use, so in essence you have put on a tyre designed for a SUV rather than a sedan (or coupe)

Anyways, I'm not here to argue and make enemies - not my thing

yeah I agree totally with the 'friends not enemies thing' - just good to have a nice 'discussion' about things.

Since I live like 5 minutes from the 5km Ramarama test I can say yes I have And that it was wrong. And you can't tell me 3 of the 5 units we have read wrong lol.

The speedos all read high - 110 indicated is 100 actual speed. I can't see any reason why a car manufacturer would not have a reason to do such a thing - technically it safer cause if you obey what the speedo says then you're going slower, using less gas and means less likelyhood for the driver to get a ticket. Effectively it gives them a sense of security they dont know about it.

And yes I'm sure they are 215/70/15. Would you like pictures? lol They're bigger tyres than the Suzuki 4x4s we have at work lol.

Side note - you probably sold my workmate the set of wheels he has on his Hilux. Pity he bent one recently.

[Nic325i 0]

You are correct in your thinking but you are making a huge assumption that BMW have designed their speedos incorrectly. Why would BMW design their cars to read 10% 'slower' than they should from factory?

Just curious but have you tried the 5km odometer test on the motorway at Ramarama. Would be interesting to see the difference between that, your GPS unit(s) and your speedo. I think we can all agree that the 5km odo test would be a good base to start from.

If you have tried it across a number of BMW's with the same GPS unit - maybe it is your GPS unit that is out? biggrin.gif

I can't believe that there would be a factory fault like this from BMW. Imagine trying to argue that in court if you got a speeding ticket! Honestly Sir, I wasn't speeding, BMW have designed their speedo's wrong tongue.gif

My E30 M325i was approximately the same - speedo read 110km/h, actual speed was 100km/h. This was on standard size wheels/tires.

Friends of mine did a research project a few years back for Navman involving driving round in lots of cars testing out GPS units - almost all of the cars (Ford, Nissan, Subaru, Toyota, probably others) had "optimistic" speedos.

[zenetti 0]

very interesting maybe now that means i can comfortably sit on 120km on the motorway without getting a ticket

[Carl 3]

Curiously, what tyre pressures you running, the bigger the profile the more variance you're going to get.

Also what exactly was wrong with the odometer test at Ramarama, was your odo out or your GPS out?

[Muzzie 0]

My E30 M325i was approximately the same - speedo read 110km/h, actual speed was 100km/h. This was on standard size wheels/tires.

Friends of mine did a research project a few years back for Navman involving driving round in lots of cars testing out GPS units - almost all of the cars (Ford, Nissan, Subaru, Toyota, probably others) had "optimistic" speedos.

CHURRRRRRRRR!!!! Back up for the world My Hiace was optimistic til I put new higher profile tyres on it. Its now slightly pessimistic, but since I have GPS then next time I'll go higher still, make it more pessimistic - help my odo

Curiously, what tyre pressures you running, the bigger the profile the more variance you're going to get.

Also what exactly was wrong with the odometer test at Ramarama, was your odo out or your GPS out?

Ummmmmmm, 32 in the back and 28 in the front I believe. Haven't checked recently to be honest. I make the gf do the weekly checks (oil water etc etc etc) so she gets in the habit of it and learns a bit, plus if anything changes she knows it might pay to scream at me til I fix it

GPS accurate to within 100m (smallest increment it displays during a 'trip'). Odo on car read higher than the 5km travelled (which backs up the theory of spoeedo reading 'optimistic').

And as said above - originally a trip from my place to gfs was said to be 80.2km, GPS said its 76.1km, with new tyres its now 72.0km (something to that affect)

Edited August 8, 2007 by Muzzie