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Tire size question on aftermarket wheels - Printable Version

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Tire size question on aftermarket wheels - rsvcc - 14-10-2015 02:14am

Hey everyone,

I'm currently running a set of 20x8.5" +38mm wheels with 245/45 tires.

I find that 245/45 aren't "beefy" looking enough, if you know what I mean. The wheel wells just aren't full enough.

So my question is, can I fit 255/55r20's (RR 20 inch wheel OEM tire size) to these wheels without any rubbing/etc? In hopes of filling up the wheel well a bit more, without fitting spacers.

Edit: A quick calculation on willtheyfit.com shows an arch gap loss of 1.2 inches with that setup i mentioned..not too bad.

Thanks in advance.


RE: Tire size question on aftermarket wheels - Steve D - 14-10-2015 06:26am

I couldn't answer the 'will they rub' question but I'd think they'd throw your speedometer reading out as well as affect acceleration although they should give you better mpg.


RE: Tire size question on aftermarket wheels - wheels - 15-10-2015 10:55am

(14-10-2015 06:26am)Steve D Wrote:  I couldn't answer the 'will they rub' question but I'd think they'd throw your speedometer reading out as well as affect acceleration although they should give you better mpg.

Not sure about that. Most speedometer readings are "happy", mine shows about 5% more. So he would propably get a more correct reading.


RE: Tire size question on aftermarket wheels - XFullFatTim - 15-10-2015 11:21am

Evoque shares its hub with Freelander2 but you say you want to fit "RR 20 OEM" - The hubs for L322 (previous FFRR and often miscalled the "Vogue"), L405 (current FFRR) and L494 (current RRS) are different so you would need to find an adapter. I'm sorry but I don't know the stud pattern dimensions or offsets but you could sign into FullFatRR.com with your babyRR sign in and ask there what the details are. You can sign into any of Martin's Forums with your BabyRR user name and password in case you weren't aware, so no need to reregister each time.


RE: Tire size question on aftermarket wheels - rsvcc - 16-10-2015 12:44am

(15-10-2015 11:21am)XFullFatTim Wrote:  Evoque shares its hub with Freelander2 but you say you want to fit "RR 20 OEM" - The hubs for L322 (previous FFRR and often miscalled the "Vogue"), L405 (current FFRR) and L494 (current RRS) are different so you would need to find an adapter. I'm sorry but I don't know the stud pattern dimensions or offsets but you could sign into FullFatRR.com with your babyRR sign in and ask there what the details are. You can sign into any of Martin's Forums with your BabyRR user name and password in case you weren't aware, so no need to reregister each time.

You're right..they are definitely different...
but, I'm not fitting the RR wheels, just the same size tire from OEM RR 20" inch wheels, ie. 255/55/r20.


I'm not too worried about the speedo reading issue, If anything, a slightly under-reporting speedometer is a good thing....my mind will feel satisfied going 5 over the limit everywhere, when in reality I'm following the limit!


RE: Tire size question on aftermarket wheels - Steve D - 16-10-2015 05:39am

With larger diameter tyres, you will be going faster than your speedo shows, not slower!
Speedo will be 7.61% out according to this: http://www.willtheyfit.com/index.php?width=245&aspect=45&diameter=20&wheelwidth=6.5&offset=40&width2=255&aspect2=55&diameter2=20&wheelwidth2=9.5&offset2=20&Submit=Calculate#content


RE: Tire size question on aftermarket wheels - rsvcc - 16-10-2015 05:40pm

Existing: 245/45r20
Speedo error = 0%
Reading at 30 MPH = 30 MPH
Reading at 60 mph = 60 mph

New: 255/55r20
Speedo error = -7.61%
Reading at 30 mph = 27.72 mph
Reading at 60 mph = 55.43 mph


this is directly from willtheyfit.com
So, in fact, the speedo would be under-reporting with the new, larger tires.


RE: Tire size question on aftermarket wheels - Steve D - 16-10-2015 06:32pm

My point exactly! A speedo that under reports means that you are going faster than it says you are!

Sorry, but you are reading that wrong.
From the same page: Circumference Existing tyre: 2288.7mm New tyre: 2477.1mm

So, for every revolution the speedo 'thinks' you have travelled 2288.7mm when in fact you have actually travelled 2477.1mm so you will be travelling faster than your speedo thinks you are going.

Have a look here: http://www.tyresizecalculator.com/tyre-wheel-calculators/speedo-error-calculator


RE: Tire size question on aftermarket wheels - rsvcc - 17-10-2015 04:19am

(16-10-2015 06:32pm)Steve D Wrote:  My point exactly! A speedo that under reports means that you are going faster than it says you are!

Sorry, but you are reading that wrong.
From the same page: Circumference Existing tyre: 2288.7mm New tyre: 2477.1mm

So, for every revolution the speedo 'thinks' you have travelled 2288.7mm when in fact you have actually travelled 2477.1mm so you will be travelling faster than your speedo thinks you are going.

Have a look here: http://www.tyresizecalculator.com/tyre-wheel-calculators/speedo-error-calculator

Thanks...I was indeed interpreting that wrong. The circumference difference definitely proves it..


RE: Tire size question on aftermarket wheels - wheels - 17-10-2015 09:50am

BUT as I wrote before, most speedometers are happy. In my case if I put on tires like the OP wants I would have a speedo that shows 2,61% to little