Wheels - spigot size concerns + tyre choice? e.g. Riva DTM

N

Newbers

Active member
 St Albans (one days march from London)
Not being one to wander too far from the trodden path I have my eye on some Riva DTM's (CSL style) http://www.rimstyle.com/alloywheels/wheel/index.html?wheel=riva_dtm_ss&colour=silver.

Would you experienced fellows kindly review my thinking?

Currently on stock 17" x 8" ET46. Love tail happy handling, happy enough with ride (sport springs at the mo - until they break again...) Like being able to swap fronts to rear at about 60% wear when they start to tramline. Currently pretty happy with Contisport (SSR 2 or 3?) runflats.

I'm thinking Riva DTM 18" x 8.5" ET 37 all round. This may seem conservative (i.e. don't get nice fat staggered rears) but handling needs to come first for me. My thoughts:

- ET46 -> ET37 with 8" ->8.5" is all but neutral.
- Square set up should retain similar handling characteristics.
- 18" rather than 19" should provide a little more protection against Hertfordshire potholes (and now sink holes! I live just round the corner from the latest one in the news in St Albans).

Concerns:

1. I was wondering about spigot diameter which is never quoted. OEM wheels are an interference fit so bolts pull the wheel up to the hub but the spigot in the middle is locating it + taking a lot of load. I once had a boat trailer loose a wheel for similar reasons and wouldn't want this on my car so I Googled and ended up here: http://www.demon-tweeks.co.uk/blog/...it-my-car-the-dt-alloy-wheel-fitment-guide-2/. They refer to the issue. Anyone any thoughts/experiences with after market wheels?

2. Could I get away with 245/35R18 tyres? Nearly an inch wider than the OEM 225 I imagine clearance would still be OK, would get a bit more kerbing protection, would have wider appearance + speedo within 1% but would they look silly & negatively affect handling (i.e. be too floppy)? I would be willing to go to non-RFT so perhaps the softer thinner sidewalls would behave similarly to harder thicker sidewalls? :scratchhead:
 
Your centre bore will be 72.6 , i would always try to avoid spigot ring fitments , especially with a Z which is very sensitive to wheel / steering / tracking issues

On the 8.5j wheels you are after then yep , 235 will work but maybe look at 40 profile for all 4 as opposed to 35 ?
 
Thanks Mr Wilks.

What's your thinking for 40 profile? Appearance, handling or similarity to standard?

From 10101Tires, 40 profile:


and 35 profile:


On this basis the 255/35 is best but I imagine that is way too wide for 8.5" rim.

Is 225/40 going to look stretched on an 8.5" rim? (I hate that look...)

Incidentally - is the standard 18" set up 8.0 front & 8.5" rear?
 
Newbers said:
Thanks Mr Wilks.

What's your thinking for 40 profile? Appearance, handling or similarity to standard?
Click to expand...

The 40 is already standard fit for your fronts & ive ran 45 on non M ( with 255 40 rear ) & would do it again
This obviously gives more comfort & reduces arch gap with no downside in performance unless you planned to break any lap times anywhere :oops:
225 would be slightly stretched on a rear 8.5j rim so upping the profile to 40 would help this
"Beetlegav" has a great pair of almost new rear 255 40 18 Kumho winters for sale at a good price
You need to weigh up your budget , that will dictate tyre choice for brand + size :thumbsup:
 
Indeed I do have some brand new tyres for sale.
Don't be put off by a staggered tyre set up, they are still tail happy with 255 on, I have 225 on the rear now and it's very tail happy.
Prefer 255 but it's not practical for me now.
 
Thanks Beetlegav & Mr Wilks,

I think I am perhaps trying to tick too many boxes!

I have no problem with buying premium branded tyres - given the miles I do, the speed I do them and the number of experiences I've had where I've felt I've got away with it (or didn't) because of my tyre choice i don't find this a hard choice. What I do hate though is the prospect of throwing a half worn pair of fronts away because they have started to tramline (especially as you can run them down to slicks on the rear without much difference to handling - in the summer at least). That's why I wanted to go for a square set up.

I'm interpreting that the sensible options would be:
1. Go for 8" rims with 225/40 all round and satisfy my miserly requirement to wring every last mm of life out of every tyre & enjoy similar handling to now.
2. Swiitch to 8" rims with 225/40 at front & 8.5 with 255/35/18 on rear. Be satisfied this is BMW spec, enjoy improved appearance, moan about binning half worn fronts.
3. Have a similar debate about 19's
4. Have another glass of wine, forget about wheels, pass out, worry about wheels next week.....
 
I think you're overthinking it to be honest.

If I were you I'd be looking at trying to mimic the OE 18" setup (8j on the front and 8.5 on the rear)

As for requiring spigot rings, I'm running them on my coupe with no ill effects (74.1mm on the wheels).
 
Thanks Neil,
I think you're right "OE 18" setup (8j on the front and 8.5 on the rear)" is prob the way to go.

Out of interest what do you do about the BMW wheel centre badges? Do they locate in and cover the spigot ring?

Also does it make it any more awkward to change a wheel?
 
Pretty sure you'll not need spigot rings firstly, but if you do, they don't affect the centre caps or make wheel changes an issue.
 
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