question about tyres in relation to wheels

[karatemaserati]

i am wanting to buy these alloys for my 3200, how do i know the size of tyre to fit?? why arnt wheels and tyres measured in the same scale?? the wheels are... 8.5x19 5/108 ET45 B73.1

http://www.goodgrip.co.uk/wheels/svf/svf_dakar/#item=37785

obviously id need spiggot rings aswell

 

[rotorheadcase]

It doesn't look like they do a staggered set in 19" You need a 9.5" or 10" rear wheel otherwise you will completely screw up the handling. The 3200 breaks traction on the 9.5" rear as it is. Going to a 8.5" rear will only make it worse and oversteer will be horrendous. Stick with the original width rims or if anything go slightly wider at the rear.

Neil

 

[karatemaserati]

cool thanks for the advice, its a shame cause they are beautiful. does anyone know of any other split 5 spoke designs that would fit?? the only other ones i know of are HRE P47's and they are an absoloubt fortune.

also going back the the original question, why are wheel measurments done like 8.5, 9.5 ect and tyre width measurments are done differently eg 225, 235 ect. and how do i convert/ work out what tyre i need for what wheel?

 

[rotorheadcase]

Wheels are generally measured in inches. For example 8.5" x 19" front and 9.5" x 19" rear wheels. Tyres are generally (not always) measured in millimetres. For example a 235/35 19 tyre is 235 mm wide (9.25") and is recommended for an 8" to 9.5" wide wheel. The /35 refers to the aspect ratio or percentage of tyre width, in this case 35% of 235mm (82.25mm) The 19 is obviously the rim size it fits... 19"

There are plenty of tyre calculators available on line that will allow you to input the standard wheel and tyre combination for your car and then give you sizes for a "plus one" or "plus two" fitment. What they are referring to is going up plus one inch or plus two inches in wheel size, for example 18" to a 19" or 20" wheel. It will then recalculate the aspect ratio to keep the rolling radius of the tyre to within around 2% of the original wheel and tyre combination. This way your speedometer will remain fairly accurate and most importantly the brake ABS and traction control systems won't throw up any errors.

I hope that's not too confusing... If you play around with an online calculator it will make things a bit clearer.

Regards

Neil

 

[Rex B]

Hi

If you are looking for 19 inch wheels try the Performance Italia web site they have 18, 19 and 20 inch sets for the 3200 and you can get a small discount on prices quoted

Rex B

 

[karatemaserati]

that is a good explanation

thanks rex will take a look

 

[karatemaserati]

unsurprisingly when looking for wheels on aftermarket sites, maserati arnt listed in the dropdown menus. jaguar however are and the fitments on the s-type, xtype and xj are identical to the 3200 bar the spiggot size which is smaller at 63.4. and the offset which can be varied anyway.

http://www.alloyguide.com/Jaguar.php


3200

Front 18 x 8 inch; studs 5 x 108pcd; et/offset 55
Rear 18x 9.5 inch; studs 5 x 108pcd; et/offset 52

Spiggot/hub boss size: 68mm


given the similarities, it wouldnt be that hard/expensive to buy wheels listed under jaguar fitments with the smaller hub size and take them to an engineers and get them bored out slightly to 68mm would it??? would be interested to hear your thoughts

 

[rotorheadcase]

A higher offset can be adjusted out with spacers but a lower offset such as the 35-45mm shown in your link to jag wheels will push the wheel further out.(which may not be a bad thing depending on the exact offset.) This will also affect the overall wheel track width and the steering may not feel as light as the original wheels. The car may feel a little more stable though when cornering with a wider track.

You will need to check that the Jag wheels you have in mind come in a staggered fitment like Maserati.

Neil

 

[rotorheadcase]

When boring out the centre, it will have to be perfectly hub-centric otherwise you'll never be able to properly balance the wheel.

Neil

 

[Alecci]

You could always do as I did: buy one set of 8.5" wide wheels and have the rear ones widened. I had my rear wheels widened to 10.0".

You still have to keep a close eye at offsets though, and depending on the wheel, widening it on the outside/face side of the wheel may be very hard or impossible if you want to maintain stock finish.

 

[karatemaserati]

alecci this sounds verry interesting, who did you get to do it and how much did it cost??

 

[Alecci]

I had a wheel workshop here in Sweden perform the modifications for me, the cost for widening the wheels was about £400, adjusting hub center bore was another £50 and custom wheel spacers about £100.

As long as P.I.D. is correct (5x108 for our cars) and you're able to calculate the proper ET/offset you can use almost any wheels as long as you find yourself a good workshop to modify the wheels.

 

[Parisien]

As ever Alex........at the top of your game....great stuff!

P

 

[Alecci]

Then there's always the option of ordering custom wheels (which I will be doing in the future, some years probably) but then the cost is a whole different story. Custom wheel sets usually start at about £4,000-5,000 so that route would be much more expensive.

My set of wheels, including modifications, and a set of new tires (245's for the front and 285's for the rear) cost me a total of about £2,000. As it's a custom modified wheel set put on a 3200 GT - where you seldom see aftermarket wheels at all - one may be permitted to say that I have a quite unique combination, which kind of makes it cheap considering the alternatives and their costs.

 

[alfettafan]

karatemaserati

Might be worth taking a look at link below to see what is available, seem to be pretty flexible on sizes...


http://www.imagewheels.co.uk/

 

[karatemaserati]

thanks alot verry helpfull, also in your avatar your car is lowered?? how have you done this just springs or coilovers??? your car looks gorgeous by the way!

 

[Alecci]

Cheers for the compliment mate. The car is not lowered - yet. I'm aiming to get a set of coilovers within a not too distant future.

 

[karatemaserati]

no probs, what is the offset of those wheels?? also does anyone know the max/min offset i can go to??

 

[Alecci]

Max/min offset is determined by the width of the wheel, so the values differ from wheel to wheel.

For myself, I took measurements from the car and constructed a calculator in MS Excel in order to calculate optimum offset for a set of wheels of the width that I wanted, and specified the values to have the wheels sit flush with the fender. One also have to take clearance of the brakes into careful consideration. For my front wheels I have about 2 millimetres of clearance, which is not much but surely enough.

Adjusting offset of the wheels themselves is not very easy, this ought to be done with spacers instead. An important note here is to use the right kind of spacers, as the wrong type of spacers may lead to excess wear of your wheel bearings.

 

[karatemaserati]

ah right, it maybe differ slightly from mine aswell being a 99 model as mine is 2001. what are the measurments of your back tyre?? do you find that having 10" restricts your choice in tyres??