914 vs the rest of Porsche

[moggy]

Looking at 15" tyres options that get me to an overall 25" diameter, my options are virtually zero. The closest I get is 245/60 15 Avon CR6ZZ @£275 each

So looks like it's down to 16 inch, these look about right:


and 17 inch, these look about right:


The tyres for the 16" would need to be 245/50 on the rear 9" wheels and are limited in choice. They run at about £150

The tyres for the 17" have alot more options for the size I need (i.e. 255/40) and run from £95 up to £170 for new, but there's a good used market for these sizes so I'm leaning towards a 17" set of black Cup1's at the moment. Now it's into the garage to figure out what ET23 on the front and ET15 on the rear look like. I reckon I'll need some kind of spacer on the back but on the fronts... correct me if I'm wrong but can't I just change this part out for wider?



Keith - that new championship looks interesting. I'm gonna take a more detailed look at that at the weekend.

[keith fellowes]

I'm in Builth at the weekend for the Severn Valley, be good to meet up again if you're in the area.In an historic Peugeot 205, yes they really are that old!

[rhd racer]

Hi Moggy

Know the section of Anglesea well - I am on the limiter in 4th trying not to turn my pants brown negotiating the kink before the braking area! Not an area that another up or downshift would help either the approach or exit in my opinion! I genuinely cannot think of any other circuit that will trouble your box - Castle Coombe would on a 2 lapped, but they run the sprint as a single lap so not an issue for you. I Rev to 6500.


Re times, we don't do a whole lap of the larger circuit ; standing start fom pit exit and finish just after the hairpin. My best in the 14 in dry conditions is a 129s lap on this basis. I guess a video review will give you an approximate lap from that without the standing start - I can probably find some in car footage to work an approximate up, but still will not be a flying lap. We do 2 laps of the smaller circuit so can probably dig out some flying lap times if that helps.

re the tyres, I can see you are in between two different and opposing problems. Apart from Ian McMath on slicks, I cannot recall anyone in a 14 going above15s and a 205 / 225 combo per my previous post. the same is true of all the early 911s competing, only the mid 70s cars might run 16s occasionally but most find 15s the best. Tyres are cheaper, more widely available in various compounds, and at a profile that gives a bit of compliance. so you can have a suspension set up that is more circuit orientated, but have a bit in the tyres to help on the hills, and able to run lower pressures. Rubber bands need to be run at higher pressures, generally, and offer much less compliance. the Boxster is on 17s, and I run 235 / 265 widths but need about 4 psi higher, and even at that they look pretty flat, and are well below factory pressures. I have just bought some track tyres and did all the same searches you have no doubt done and arrived back at tried and tested toyos; my thinking being that for hills I will get lightweight rims and Kumhos for the hills next year. This is another consideration - first principles are weight loss, and unstrung at that, so the smaller wheel will be lighter.

I would also say that with 140 odd hp absolute grip is probably less of a concern than if you had 240 - so I would suggest a 7&8 or 7&9 combo with the Kumhos in super soft compound (because you are very light with a 4) with spacers will give you a night and day different grip level to current, be cheaper, and give you lots of suspension dev't choices as you find your groove.

All my opinion of course, so I hope constructive. If you make Loton, you can try the Boxster wheels on your car, or if you give me notice I can bring a pair of the 7s & 8s off the 914 to try before you buy....

just let me know, happy to help,

cheers
wayne

[moggy]

I think I have a plan brewing on the wheels and tyre front. I'm going to go with 2 sets: one for hillclimbs, the other for circuits.

Hillclimbs - I've got a set of 7" cookie cutters in the garage which will suffice for now. As acceleration is king rather than top end I can afford to go with 50 profile tyres (e.g. 215/50 15 Dunlop DZ03G) which will mean it should accelerate like a scalded cat but won't see north of 100mph. The lower profile tyres will also give me better cornering stability.

Circuits - I'll go with a cheap 17" wheel which will allow me to keep a 25" rolling diameter and maintain the present max speed. I'll go with 7" on the front and 9" on the back with something like a 255/50 17 Dunlop DZ03G on the backs (which gives me exactly a 25" rolling diameter) and 215/45 17 on the front.

Having the same wheel/tyre combo for both types of events would be a compromise with my gearing. Splitting it like this seems to make sense to me. Whadya reckon?

[jwhillracer]

Sounds right to me! If you are buying new tyres, I would look at the super soft Kumho's all round for hillclimbs. Max grip for your £££££

JW

[rhd racer]

Sounds like a plan Rich

As JW says, everyone uses V70rs on the hills for a reason!

Cheers
Wayne

[moggy]

I can find V70ahttp://www.camskill.co.uk/m12b102s661p4 ... OFT%29_TL_ but not V70rs. Am I missing something? are these the same tyre you are referring to?

[rhd racer]

Yep, that's them, sorry!

[moggy]

So last night the conversion from rally car to track car started with a diet. 50kg was taken off the car in the form of front and rear skid plates, rear skid plate mount and the spare wheel/tyre.

[rhd racer]

Remember there is a minimum weight in P4, which I think is 1025kgs from memory, wet with driver.

cheers
wayne

[ollieg]

So last night the conversion from rally car to track car started with a diet. 50kg was taken off the car in the form of front and rear skid plates, rear skid plate mount and the spare wheel/tyre.

…think you're going to need a new drawing of your car!

[moggy]

Managed to get a few hours on the car yesterday. Fitted the new wheels I picked up off ebay. 9 inch on the back and 7 inch on the front. Cup1 replicas with ET25. I need to use spacers to get the right back spacing. Anyone know where to get longer wheel studs from? and any tips on getting the old ones out and inserting new ones would be appreciated. The rears will probably be more of a PITA as the studs are welded on from the back as they are a 4 to 5 stud conversion

[rhd racer]

I think mine were from either Porscheshop or Design 911. Mine weren't welded like yours, just splined like your fronts will be. I made a very Heath Robinson jig to hold the hubs steady whilst I beat the cr@p out of them!

unfortunately the jigs were taken away by the Idiot Home Mechanic Police to be destroyed after I had finished

Hopefully see you at the weekend

cheers
wayne

[jwhillracer]

The rears will probably be more of a PITA as the studs are welded on from the back as they are a 4 to 5 stud conversion

If you can find a pair of rear hubs from a pre-74 911 (ie one with steel banana arms) that will make the process a lot simpler.

JW

[moggy]

Thanks for the tips guys. I will be back in the UK early hours of Saturday so I hope to see you on the weekend. I'm virtually ready now to join you guys. My new race licence came through while I've been away and the bits and pieces on the car are virtually all converted from rally car to race car now. So I'll plan to find out what I have to do to join the party and come racing at the next event.