15" MIM's grrrr!

[ropeman]

Managed to get a very nice set of 15" MIM's. So I thought quick change from my 17" team motorsports to the new rims would be easy........

I bought the car with the 17's but haven't enjoyed the ride and not to keen on the look. The MIM's went on the rear with no problem (325i rear discs), but on the front they foul the front face of the caliper (I have hispec 4 pots on the front). I can get over this using a 10mm spacer, but I'm not a fan of spacers.

So the only options I can think of is:

1. Change the calipers back to stock - not going to happen, I'm running 210bhp and plan to add another 70 - 80bhp to that in the next couple of weeks.

2. Get the insides of the MIM's machined to fit, but I'm thinking this isn't a very safe option - thoughts?

3. Suck it up and run 10mm spacers.

Anyone have any other thoughts? My goal is not to have the wheels poking noticeably out of the arches, or the front track looking odd to the rear.

[andysheep]

I have seen people grind on calipers before(mostly corners) but without knowing inturnal daimeters its a shot in the dark i probably wouldnt do it and without a repaint they would look shit,maybe get a blueprint of the caliper design?and see if there is any wiggle room there?

[HairyScreech]

NOPE, seen popped aluminium callipers from grinding as the walls were ground too thin and the alu could not hold the pressure any more.

A lot of race style aluminium callipers have very little spare meat in the walls to keep the weight down, just enough to give a decent safety factor and that's all. Removing the lettering if it is the raised lettering CNC machined style of calliper is often fine but any time your cutting into the wall your risking it.

Much better to use a 10mm spacer. If you are worried about spigot location then make up some billet alu centre caps to extend the centre bore like I did for my 5 stud.

Another option may be to speak to WMS about some of their callipers, (Kerry is on here) They have tried them behind 15" MIM wheels in the past.

[ropeman]

Yep agreed. Ive heard some nasty stories from caliper grinding.

Right so how badly do I want MIM's on my car...?

The rears fit and look great, but even just moving the car round my workshop (flat floor) they slightly rub the arches. So I'm going to have to roll them. I guess a 60mm drop on et13 is just to much.

I've tried (before I wasted money on hubcentric spacers) using a standard 10mm spacer to see how the front wheels line up. And they look crap + they rub the inner arches on turn in, and the wheel weights now hit the caliper when the wheels turn!!

So I'm back on the 17's again and not enjoying it. The 17's obviously work as the et is greater so sit further under the wheel arch + the wheel spokes are curved from the centre back to the rim (MIM's are dead flat) so this allows clearance for the caliper.

So the options are

1. Give up
2. Find a 15" rim that is better suited - could get expensive as its a bit of a guessing game. The type of thing that could work is an ats cup?? Don't really like them though, but the spokes are the right kind of shape to clear the caliper.
3. Speak to WMS and see how much there setup is and hope I make some money back selling my setup.

[jimmyspeed]

If they are mim 1900 why not have a look at a set of Hartge 16 inch ones as they are quite a similar style. Maybe a bit more expensive though.

[DHFiS]

So the options are

1. Give up
2. Find a 15" rim that is better suited - could get expensive as its a bit of a guessing game. The type of thing that could work is an ats cup?? Don't really like them though, but the spokes are the right kind of shape to clear the caliper.
3. Speak to WMS and see how much there setup is and hope I make some money back selling my setup.

I think this sums it up

[HairyScreech]

What 17" wheels are you using, when I switched from the 15" bbs to a 5 stud setup and the BBS RC41 the weight increase was only 1kg and made little difference to the way the car drove, IIRC they were 18 and 19kg respectively.

Your next best option is to find some suitable 16" wheels.

[broadie]

Not sure this would help!
Are they genuine mims I was informed that some of the copy's require spacers even on standard brakes.

[ropeman]

They're MIM 1900's, not sure if they're genuine? How can I check, will they be stamped somewhere?

So I've printed off the WMS .pdf for checking wheels to calipers and they don't fit I used the smaller disk option, but instead of my current problem these will rub on the edge of the caliper rather than the face.

I guess next step is to phone hispec and see what 15's they know that fit.

I'm running 17" Dynamic Motorsport. I don't know the offset as they've been powder coated and the paint is thick and completely blanked out where they are stamped (.........I think that's where they're stamped). I'm also running HR cup kit with a 40 / 60 drop. Weight isn't that concerning, its more:
1. I don't really like the look of my 17's
2. I love the look of the Mim's, but this isn't going to happen so I'll probably need to sell them on.
3. I much prefer the look of e30's on 15's
4. I think the extra tyre wall will make for a much nicer ride.

I'm not totally aposed to 16's, but it's the same issue, without testing them on my front brake setup I won't know until I've bought them whether they will clear or not. Think I need to speak to hispec...... Or start a new 'hispec Caliper what wheels do you run' thread.

[jimmyspeed]

They say made in Italy on the inside for genuine ones

[HairyScreech]

Have to say I did not find much of a decrease in comfort going to other way to you, I went from 205/50/15 to 215/40/17 which I was expecting to be a bit rough as they are practically a band of black paint compared to the 15" tyres.
The smaller diameter of the 15" tyres might have been the deciding factor as a large diameter always has a better angle of attack at a pot hole or ridge in the tarmac.
I don't think I could ever run 205/55/15 tyres again as the side wall flex was just too much.

Weight is worth considering, a lot of the horror stories with 17" wheels are related to the weight of the wheels, some aftermarket wheels and tyres come in at ~25kg a good 6kg per wheel more than the stock e30 ones, the dampers are valved with a specific mass in mind and the heavy wheels can really effect the damping and thus ride quality, the weight blows through the damper travel on bump makes things feel "crashy".

It might be worth weighing your 17" wheels as I know my friends 4 stud 17" Team dynamics were really heavy.

What dampers do you have on?

Is there a disc you could use with your Hispec callipers that has a deeper hat height? it would allow you to move your callipers inboard.

Any pictures of your setup?

[ropeman]

They say made in Italy on the inside for genuine ones

I'll have a look. Not that, that will make them fit ;) But good to know.

[ropeman]

Have to say I did not find much of a decrease in comfort going to other way to you, I went from 205/50/15 to 215/40/17 which I was expecting to be a bit rough as they are practically a band of black paint compared to the 15" tyres.
The smaller diameter of the 15" tyres might have been the deciding factor as a large diameter always has a better angle of attack at a pot hole or ridge in the tarmac.
I don't think I could ever run 205/55/15 tyres again as the side wall flex was just too much.

I've not heard this before, agree with the sidewall flex, but personally I've always found handling to be better with a smaller diameter wheel, obviously there are limits.

Weight is worth considering, a lot of the horror stories with 17" wheels are related to the weight of the wheels, some aftermarket wheels and tyres come in at ~25kg a good 6kg per wheel more than the stock e30 ones, the dampers are valved with a specific mass in mind and the heavy wheels can really effect the damping and thus ride quality, the weight blows through the damper travel on bump makes things feel "crashy".

It might be worth weighing your 17" wheels as I know my friends 4 stud 17" Team dynamics were really heavy.

I'll check this out. Unsprung weight obviously makes a big difference when you're talking those figures.


What dampers do you have on? H&R cups

Is there a disc you could use with your Hispec callipers that has a deeper hat height? it would allow you to move your callipers inboard.

That's a really good point, but that would also mean changing the hub or spacing the calipers some how, not sure where to start with that.....?

Any pictures of your setup?

I'll post some next time I take the wheel off

[HairyScreech]

One thing to note there, by bigger diameter I mean total diameter, the 205/50/15 has about 1cm less on the rolling radius vs the 55/15 or the 215/45/17.

Wheel weight can have a huge effect as it is right out at the furthest point of the suspension, it is mathematically the most significant item as it it the only thing that moves 1:1, all other components are inboard and move in an arc thus moving less, the ARB ends only move something like 0.6:1 and the E30 wishbone only seems to have about 30% of its mass unsprung.
Mass on the weeks easily beats mass in any other part of the suspension.

The H&R cups would have been designed around the stock wheel weight +- a bit. Stock weight is something like 17-18kg.

To go for a deeper disc you would need some brake brackets that allow the caliper to fit further towards the center of the car, might not be possible, depends on the design of the brake kit.
The other option is a narrower disc, as you could narrow the calipers to suit, some of the kits with floating rotors use 35mm discs, fine for a touring car but an e30 could get away with a thinner disc just fine, especially if its a road car.

[ropeman]

Right problem solved I've bought some of these! http://m.ebay.co.uk/itm/B-Star-RA-8x16- ... nav=SEARCH

Not MIM's but had to let go of the idea.

Looked on the inside and my MIM's say made in England.

Thanks for all the advise.

[HairyScreech]

The R5 picture there is priceless.
The Mc D in the background just makes the picture.

Looks a very clean R5 though.

[ropeman]

As you say 'priceless'. Nice wheels though and pretty light, following your previous advise.