Tire Clearance GTV

axlejor · #1 (**permalink**) 10-20-2005, 06:46 PM

I posted this in another thread under autocross but got no response, I thought I'd try again with new title.

Does anyone have experience with fitting a 225/50R14 on a late GTV (74). I currently use Kuhmo Victoracer in a 205/55R14 and still have plenty of room to spare. Keeping in mind I'm using 14x6 inch Cromodora Daytonas. I would like to run the Kuhmo V710s next season and they make it in this 225. I'm just not sure it would fit.

My fenders are not rolled, the car is lowered about 2 inches and has 3 degrees negative camber.

Any thoughts?

JoeCab · #2 (**permalink**) 10-20-2005, 10:02 PM

A friend of mine ran 225/50-14 Toyo RA-1s on his '74 GTV without a problem, but it was not lowered. I don't think you'll have any problems at the front, however the rears may be an issue depending on wheel offset.

Also, I am not sure you will see much benefit with the 225s on a 6" wide wheel. They would work much better on a 6.5" or 7" wide wheel.

Joe

axlejor · #3 (**permalink**) 10-20-2005, 10:26 PM

Thanks for the input Joe. I'd love to go to a 7 inch Panasport, but don't have the $. I use this car for autocross so I think wider is better either way, this is two sizes wider than I currently run.

**wctouring#7** · #4 (**permalink**) 10-21-2005, 07:13 AM

Even if the tire does clear, the problem you will have is the pinching of the tire. Running the 225 on a 6" rim will give you less of a contact patch on the ground (unless running too low of tire pressure) than running the 205. Running the 225 at normal recommended pressures on the 6" rim will cause the tire to crown and you will be essentially running on a "strip" of the center of the tire. If you lower the pressures to get a good contact patch, you will then start having a lot of sidewall flex and adverse handling issues. I'd advise to stay with the 205 until you can afford a 7" rim.

darth dino · #5 (**permalink**) 10-21-2005, 11:40 AM

Alex,
I am running 205/55-15 on 15x6.5 panasports obtained from AR Ricambi many years ago. I forget the offset, but it was the same front and rear. With the car lowered 1.5", the front tires rubbed on the front fender lips, so i needed to have the inner lips rolled for clearance. In back, the tires rubbed on the inside of the fender well, so I added 1/4" wheel spacers, but they still rub while going over big dips with a passenger on board. With 225 tires on appropriate size rims ( approx 7.5" wide ), the offsets seem to me like they will need to be different front and rear, or use big spacers on the rear.

wctouring#7 is right - 6" rims are way too narrow for 225's. 7" is ideal for 205's, but can usually be used on 6" OK.

I know using that size tire can be done, because other Alfa autocrossers and roadracers are using 225's.

david rivkin · #6 (**permalink**) 10-22-2005, 08:38 AM

JoeCab & wctouring are right, but why? The ideal rim width equals the nominal width of the tire for maximum handling. Back in the middle 60's, Autodelta used Dunlop Racing Tyres of 5.50x14 on 6" rims, achieveing over 100% on a tire width to rim ratio.

Lets see whats now, with three sections: 195, 205 & 225. Convert to inches. We have 195=7.68" 205=8.07" 225=8.86" Now we divide that into 6.

195=78% 205=74% 225=68% Since a tire width should be at least 75% of the rim width we see that the 205 tire is the widest that will work correctly on a 6" rim.
The 225 is below handling standards. The 195 is best. For myself I use a Yoko A032 195/60x14 on a 6" rim for my vintage racing GTA. On my track day GTV6 I use a Kumho Ecsta V700 225/50x15 on 7" rims.

If at present you cant buy 7" rims stick with 195's or 205's. You must decide, are after speed or looks.

David
66 GTA & 81 GTV6 2.5

axlejor · #7 (**permalink**) 10-22-2005, 05:34 PM

Thank you all for your thoughtful responses. Its sounds like I'll stick with the 205's for now, until I am able to upgrade to a wider wheel. The grip is already great and with the Kuhmo 710's it will be even better. Sometimes you just need people to tell you what you already know.

wirelessjunkie · #8 (**permalink**) 10-22-2005, 09:38 PM

Since we are on the topic of tyres, has anyone tried fitting different sizes for front and back. Maybe comething like 195/60/14 front and 225/50/14 rear? I'm using a set of 6.5J x 14" rims. I was thiking of fitting these to my Giulia Sprint GT project as the car has flared rear arches.

david rivkin · #9 (**permalink**) 10-23-2005, 01:52 PM

Very wide tires at the rear will make your Giulia Sprint GT look like a cartoon but add very little or nothing at all to its handling. There are basically two reasons that I can think of for very wide rear tires. One, to absorb extraordinary amounts of HP as in racing Cobra's or prototype Ferrari's - or two, to correct or aleviate a rear-engine oversteering problem a la Porsche.

The Giulia Sprint-series of cars are well balanced machines and assuming that Autodelta knew more about that series than either you are I, I would bet that your engine, if in 1600cc race form will not develop more than 155-160 HP and if in 2000cc form, not more than 175-190 HP. So there is no need for wide rubber anywhere.

No doubt wide rear rubber looks great to eyes that have grown up in this computer age - but - wide rubber absorbs more power, creates drag, can unecessarily change rear axle gearing and creates unecessary understeer, everything needed to slow your car down.

Unless you are dumping a small-block Chevy into your Alfa, stay normal.

David
66 GTA & 81 GTV6

2000gtv-sng · #10 (**permalink**) 11-01-2005, 05:53 AM

This has been a most enlightening read. I drive a 2000 GTV and am thinking of switching from 185/65/14 to 195/60/14 for my trackdays, but I already have some ground clearance issues (speed bumps) as my car has the Harvey Bailey handling kit from the UK (lower by about 1 inch). Any thoughts on whether the 195/60 will make matters much worse?

david rivkin · #11 (**permalink**) 11-01-2005, 03:22 PM

I use 195/60x14 Yoko A032R's on my vintage racing 66 GTA. There is 4.25" ground clearance even with the deep sump particular to these cars. Sometimes I will drive this car to our NYAROC Sunday Breakfast - but - the driving is on limited access Parkways and smoothy suburban roads. No speed bumps in the area.

However, I think the car will be OK on your 195's even with the lowering kit. If you are still worried, why not install the oil pan guard, available through all the supply houses that advetise in the Alfa Owner. There is an additional advantage to the pan guard. Since it bolts to the frame forward of the steering box, which is the weakest part of the chassis, it should assist in stiffening the frame, which in turn will aid in handling.

David
66 GTA & 81 GTV6 2.5

2000gtv-sng · #12 (**permalink**) 11-02-2005, 03:48 AM

The other thing I've been wondering about 195/60/14 is that as far as I know, 185/70/14 is the closest to the original tire diameter for early 70s GTVs. 195/60 is an inch less in diameter than a 185/70. Doesn't that have a big impact on gearing, with benefits in acceleration but loss of top speed?

Geoffz · #13 (**permalink**) 11-11-2005, 05:48 PM

I have a set of Campagnolo Turbines 5-1/2" X 14. (1974 GTV)
Looking for a set of tires that would be ideal for street and track day time trials. With those size rims is it better to go 175/185/195 ? And what brands? Bias-ply or radial? Thanks in advance!

105.30 · #14 (**permalink**) 11-16-2005, 11:00 AM

I prefere for sporty driving 195/60 Bridgestone RE71 on 15 inch wheels.
I've bought in Germany a set of four aluminum Rondell 26 wheels (modern production) 7 x 15 with offset 38 mm.

A very good and original combination is 185/70 on 14 inch with road racing tires from Avon.

GAalfa · #15 (**permalink**) 11-19-2005, 07:44 AM

Is that negative offset. Are the fronts the same as rears?