Centre bore

[AlVal]

Does anyone know how I'd go about getting the centre bore of a wheel increased to the 71.5mm the cerb needs, if using a wheel with smaller centre bore (and assuming it wont adversely affect structure). is a lathe the tool required? what kind of workshop would have the tool required? an engineering company of some sort? just wondering where i could take a set to have it done.

[Manfred]

AIVal, Yes, what u need is a big lathe engine. I did it for another car. But always consider the fastness of the rims, I reckon a few millimeters is not really a problem. Donnu whether you find someone that does much more, except he´s already in prison

[Steve_T]

Al, you're better going about it the other way around. Get wheels with too large a centre bore and get some spigot locating rings made up to centre the wheel on the hub, before you torque up the wheel nuts.

Steve.

[ridds]

Either a lathe or a Vertical Mill (I'd prefer to use the latter as it doesn't involve 15Kg of spinning metal and not many people have massive lathes).

[plasticman]

Alot of the after market wheels have a large bore and a spacer so you could easily end up buy or making some new spacers . This happened to me last week , I bought a set of OZ superlegarras which turned out to have a 75mm bore .Incredibly the wheel and tyre combination weighed 16lbs lighter (each)than the spider one !

[AlVal]

I ask because there are many rx8 wheels on the second hand market.

They're very cheap, they look good, good availability, 18s, correct pcd, offset and rim width look pretty much perfect, only centre bore is around 67 so would need a bit of boring out. if the boring was cheap work they'd make a really sensible option. Grind out the mazda logo while at it I guess

[Erich Stahler]

AlVal said:

I ask because there are many rx8 wheels on the second hand market.

They're very cheap, they look good, good availability, 18s, correct pcd, offset and rim width look pretty much perfect, only centre bore is around 67 so would need a bit of boring out. if the boring was cheap work they'd make a really sensible option. Grind out the mazda logo while at it I guess

go to one of the places that refurb wheels, they will almost certainly have a lathe with a big enough to take a wheel in the chuck - i got my wheels centers opened up by a couple of mm by such a place.

[touching cloth]

Don't think they are the correct offset, RX8 is 50mm where correct Cerb offset it 35, would need 15mm spacers theoretically, which is pretty hefty.

[AlVal]

touching cloth said:

Don't think they are the correct offset, RX8 is 50mm where correct Cerb offset it 35, would need 15mm spacers theoretically, which is pretty hefty.

remember an offset is only valid for a specific rim width, once you change the rim width, you'd actually have to increase the offset of the wheels to keep them at the same "flushness" at the outer edge. otherwise if you increase rim width and dont adjust the offset, youll have a wheel that sticks out further as well as sticks in further. As these are 8j wide, that would push them out a bit more than original wheels, meaning you wouldnt have to space out 15mm , probably end up more like 10mm further into the arches than original, and that 10mm will get eaten up as soon as you increase tyre width past the OEM 245

[touching cloth]

Not sure I agree with that, increased width is usually preferred to be spread evenly unless you are changing other characteristics of the geometry and suspension set up, a few mm tweak here or there maybe if clearance of an arch is an issue, but all other things being equal then it's usually better to balance the spread evenly, basically retaining the same offset.

However regardless, it's front steering clearance that will be your worst enemy here, Spiders already cause grief with wishbones with a 42mm offset, yes they are 0.5" wider rim but if you are sticking jumbo tyres on to try compensate for wrong offset (and it is wrong, whichever way you look at it), then wheel width becomes irrelevant anyway - if you "fill out the arch" in one direction with giant wide rubber, then at the same time you are adding further to your clearance problems on the inside edge - I would guess you will end up having to fit lockstops that are even more restrictive than those used with Spiders, giving you a turning circle of a small oil tanker. To my mind it's just to many compromises - you could seriously compromise handling even with a probable decrease in overall track (there is afterall only so wide a rubber you can fit to an 8" rim).

I only say this, cos I went through the whole dilemma. Was sure I could find a way to fit some cheaper rims onto the car. Ended up tearing my hair out as everything seemed to cause one problem or another, ended up deciding that it wasn't worth trying to find shortcuts with a car like the Cerb and bought some SP12's - expensive, yes quite, but I know they are bang on.

[plasticman]

I think you will find ,if you look around , wheels that are much closer to the correct offset . I have a set of 8" rims on my T350 that have a 40mm offset . On the rear i had a larger spacer made to move the hub away from the upright and moved the caliper out accordingly , quite easy .

[AlVal]

I get what you're saying TC, valid points all. I had bought a set of volk sf challenge which were just about perfect, but the deal fell through (the stickers didnt look like original ray's stickers normally do) they were probably fakes blah. I kept away from the sp12 only because too many spokes for cleaning. I've now finally got a set of crazy expensive (about £2000) ray's engineering gram lights 57s pro, with a cool titanium rim, found them on fleabay like new at about half of the new price http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&am... . the offset is +30 on an 18X8 rim, so let's see how that works out, as you say its not all about keeping the outer edge of the wheel flush, you have to consider inside clearance too, and ideally keep the offset original if you have the clearance on both sides to increase rim width. my tyres arent as wide as some might have gone for, so that might help a bit with clearance (235/40 on back, 215/35 on front)