Looking for advice on spacers

[pbr67_zed]

Currently running 19" wheels with Bridgestone runflats on my e89, and finding the ride just way too hard for my liking, so I'm thinking of dropping down to 18" wheels with non-runflats.

Been looking at a set of refurbed 108's, which will obviously require some spacers, but just want to check I've got my maths right!

Existing wheels are:
Front 19" x 8J ET29 with 225/35 rubber
Rear 19" x 9J ET40 with 255/30 rubber

108's are:
Front 18" x 8J ET47 with 225/40 rubber
Rear 18" x 8.5J ET50 with 255/35 rubber

I think I need 18mm spacers on the front, and 4mm on the rear to keep the inner clearances of the wheels in the same as they are currently, or 16mm spacers on the rear to keep the outside edges in the same plane as they are at the moment. Can anyone confirm? Guess I could probably go for 15mm or 20mm all around to keep things simple.

I've never used spacers before, so is there anything in particular I should be looking for. Hubcentric is obviously the way to go, but is there any preference over using spacers that bolt onto the hubs, with the wheels bolted onto the spacers, rather than spacers with longer wheel bolts?

Are wheels with spacers the best way to go, or would I be better looking for wheels with offsets designed for the car?

Sorry - that's a lot of questions!

Cheers.

 

[mr wilks]

Change your tyres to Vred Vorti or Uniroyal Rs3 & you will feel like you have dropped to 18s .
Probably cheaper than the 108s with suitable spacers ( which imo will not be pretty on a E89 )
I would go 225 35 19 fronts / 255 35 19 rears

 

[Mister T]

You're correct with the spacer sizes (16.4mm on the rear to have it sit the same).

However, I'd also just suggest changing the tyres...

 

[pbr67_zed]

Thanks for the replies

Other than the aesthetics is there any reason to stick with 19's over 18's (or even 17's)? My current wheels are 296's, and one of the rears has already cracked and been repaired, so I'm concerned that even with non-RFT's it will go again. I think of the car as more of a GT rather than a sports car, so don't tend to explore the limits of the handling.

 

[Peterboroughdave]

I would follow Mr Wilks advice, Exactly as his comments in his reply to your post above.

We fitted UniRoyals (non run-flats) with the deeper side wall (sizes as Mr Wilk's recommds) onto my wife's 3.0 E89 which has the 19" 326m alloys.

Much smoother ride and no longer concerned about cracked wheels.

Dave