Re Offsets (Fao Tom) thoughts please

[nico]

I'm beginning to question this brembo conversion (which is a little late in the day considering I've already bought one complete set) since I've been trying to determine (after the guy I bought the calipers off did warn me) how close to the spokes of my alloys, the calipers would sit.

After much sketching ive calculated that for my alloys to permit the brembo calipers sufficient clearance, I'll need to use min 12mm spacers with my alloys that already have an offset of 38.

If indeed I opted to continue in this pursuit of fitting Brembos, besides having a new set of wheel bearings to hand (and possibly a couple of hundred more pounds to widen the arches if need be) what would you say are the implications for handling? 12mm isn't huge, but on top of the 38, I duno what that adds up to in terms of detriment to performance.

My main concern is that the 17s I've got already sit wide and fill the arches nicely (more so than I originally expected), so that 12mm could mean arch widening is otherwise necessary.
Q. Are hgt arches simply flared more ie. would HGT arches go on a HLX?

 

[Tom]

12mm is a LOT!

What wheels have you got? Are they quite deep dish?

 

[nico]

yer, they are quite dishy, and my brothers arn't any better.

How does might this additional amount of offset on the fronts affect 'road holding' then Tom? (I'm aware that bearings and butter are probably foremost in your mind )

My same alloys on a non hgt with smaller disks would (only) warrant a min 10mm spacer as it happens. I finally met Ribz yesterday, but I didn't ask him what size spacers he did use.

Thing is, this also brings into playb the issue of the bolt lengths and getting wobblys and the locking variety to fit. Without sufficient thread on the wobblys n lockers (doubt ones with an additional 12mm are available), I'd have to approach FK for some of their spacers (which bolt to hub, and have inserts to accomodate the standard (wobbly) bolts), but at least I know they are available like that if I do opt to get em.

I know what your thinking Tom. It's an awful lot of bother for bigger brakes I'm inclined to agree

 

[Tom]

12mm is alot, and those adapters which bolt to the hub and then have threads for the wheel bolts are pure evil IMO. I can't think of anything thats more dangerous.

It would be easier and safer to change to a wheel with a shallower dish.

Or get some custom discs made up.

 

[nico]

i perhaps should have heeded the guys warnings when he pointed out that there were to his knowledge only about three wheels with our fittment on the market with sufficent clearance to allow the brembos.

The disks are an extra 5mm further out from the stock hgt 284, and then the claipers project a further 62 whereas the hgts only stick out 24!
I dread to think how much bespoke disks might cost.

You've mentioned it before Tom (but I've since forgotten) what the actual effect is of having a wider track at the front. How would it affect handling??

Incidentally, the wobbly bolts Motorprats sent are approx 24mm and 28mm for the lockers. It may depend on the alloy wheel I suppose, but might that 28mm be too long considering the std ones are only about 20mm?

 

[Tom]

The offset is more to do with steering, you'd get more bump steer and worse tramlining.

Anyone know what wheels Allan has on his turbo brava? He has the wilwood 4 pots.

 

[nico]

Sorry Tom

What is bump steer and what is tramlining??

 

[Barakka]

Re: Sorry Tom

Bump Steer is when small bumps in the road surface cause the steering to alter direction. Also defined as the tendancy for a vehicle to swerve to one side when hitting a bump in the road surface.

Tramlining is when the car follows ruts/grooves/abnormalities in the road rather than going where you tell it to.

Neither is good really.

 

[Tom]

Re: Sorry Tom

What he said

Discs on custom bells will set you back about £200/side

 

[nico]

Re: Sorry Tom

200 a sides not crazy i suppose. Is that a guess Tom? Where do you know that might do custom spec parts such as disks? FK do an almost range, I could ask them.

Affects of spacers on steering sounds pretty harmless. Incorrect camber or alignment I'm sure must contribute much more to such deviances than marginally increasing the offset!?

My main concern is how much the wheels would stick out. That 12mm would mean **** will fly all up the side of my car! Even if got the arches widened (I don't even wanna think about the cost of that) I'd have to flare them right down to the base of the wheel arch (could look pretty c l tho!)

 

[Tom]

Re: Sorry Tom

Its an educated guess going on the price of suitable discs and partly machined bells. Replacement discs would be

 

[doofus who knows diddly!]

Re: Sorry Tom

Is castor to do with the alignment then?

 

[Tom]

Re: Sorry Tom

No, thats toe.

http://www.grampianjec.com/wheel_align.htm

Castor effects self centreing of the wheels.

 

[nico]

Re: Sorry Tom

Gud job you gave that link or I'd think you were makin this up!

 

[nico]

don't put that stick away just yet Tom!

Are the upper and lower ball joints of the steering pivot axis not vertical then because of the steering rack?

If suggests perfectly vertical camber is ideal. It dosn't actually say WHY a bit of toe-in is a good thing?

I was thinking about how the a difference in track width might be more of a factor (differetn off-sets front to rear) and how this could perhaps be detrimental. But if more of a difference was not a good thing, then why for the 20v did they shorten the rear width from 1447 to 1430, and yet widen the fronts from 1445 to 1471 !??

 

[Tom]

Re: don't put that stick away just yet Tom!

Keeping a zero camber angle means the tyre is always flat to the road. As the body rolls the camber on the outer wheel will go positive hence why its usually set at about 1deg negative.

Mcpherson strut suspension is also shite when it comes to camber angle vs suspension compression.

"At the front tyres, toe-in improves straight-line stability"