Re: Changing wheel size from 18inch to 17inch C-GT

Query Approved

The chassis is designed to work with 18inch wheels. Going a size down might upset the handling substantially. I wouldn't risk it. And if you do plan to experiment, please do keep the originals with you in case you have to revert to stock.

Also be careful going the alloy way from spokes. If you keep making your bike more practical, it will go from a cafe racer to a modern day motorcycle

Re: Changing wheel size from 18inch to 17inch C-GT

I wanna give a detailed reply to this thread on what I've found out. Will do it once I have spare time.

Re: Changing wheel size from 18inch to 17inch C-GT

Well in my hunt for understanding what impact will occur if I change the wheel sizes I went all over the internet & read may blogs, posts and forums. Conclusion was tyre size is very important but minor changes doesn't really have a big impact. In essence.... the final wheel diameter (rim+tyre height) is what matters and not rim size as such.

Also what I realised is that calculating the diameter of the wheel after the tyre size is taken into effect is not as straight forward as calculating rim diameter. Thing is when we say specifically rim diameter it's a simple 2pieR. But if we have to calculate the diameter of a tyre...say 17inch tyre 110-90 size, then it's a whole different ball game since the numbers here mean that 110 is the width in mm and 90 is the sidewall ratio. so in effect it's not really easy to calculate diameter.

This particular page was helpful in calculating the entire wheel diameter (rim+tyre size) Tire Diameter And Circumference Calculator. This eased the life atleast for calculation purpose. it even gives you circumference values.

For GT the diameter with stock wheels measures as follows: these are 18inch rims
Front - 100/90_ 18 = 25.08 inches Circumference = 78.813
Rear- 130/ 70_18 = 25.165 inches Circumference = 79.058

Now I tried and reverse calculated what size tyres I'll need on 17inch rims to match closest to each front n rear stock wheel sizes. And results were as below.

17 wheels -
Fr - 130/80 = 25.149
Rr - 130/90 = 25.189

Now these sizes are ideal from sizing perspective but not from handling pov. Having those thick front tyres will seriouly make a huge difference in negotiating city traffic. The other issue could be availability of tyre such a size.

So real world options are to be considered, in the range of 140 or 130-70/120-80 for the rear and 120 or 110-90 there abouts, there are a few options in MRF, Michelin & Conti in that range. and if we for example consider the rear
140/70 - 17 Mich Pilot sport / Conti Metro = 24.717 inch Circum=77.651 which results in 0.432 inch difference in total height though about 1.4inch in circumference meaning I'll be tad-bit slower and cover tad-bit lesser distance.

At the front is where the difference will be a little larger since getting taller tyres is a bit of a challenge.
100/80 - 17 Mich Pilot Sport 23.3 inch while a Conti Metro 100/90 will give 24.087 inches. again about 1inch difference in Diameter.

Now when a 1 inch difference is at diameter then on the road height difference will effectively be 0.5inch since what matters is the height from the axel to the tyre bottom ie. Radius = Dia/2 = 0.5inch. which is not very large and will have negligible affect on handling.

But while I was earlier preferring 17inch alloys so as to get a wider choice of tyres after all this study I've come to realize that if I need to keep the height effect negligible in handling my choice of tyres are limited. So another option is to simply get 18inch alloys and checkout what best options I'm able to get with 18inch wheels since I see a few Michelins, Contis, MRFs and Ceats being available.

others can let me know their views on this... and I hope my detailed post will help someone else in their tyre size change quest.

Re: Changing wheel size from 18inch to 17inch C-GT

Like i said earlier as well. Stick to 18.

In a hypothetical situation, even if your outer diameter remains exactly the same by getting the exact size of tyre you require for 17 inch rims, the proportion of metal to rubber will change greatly. If your stock is 80 rim and 20 rubber, then your new might be 70 rim and 30 rubber. That is a big difference. A different rim size will more likely require a change in design of the chassis!

If you want, you can put slightly higher aspect ratio tyres (compared to stock) on your 18 inch rims. This will help on bad roads, it will protect the rim.

Re: Changing wheel size from 18inch to 17inch C-GT

Can you guys point out options for 18inch or 17inch alloys which will suit the gt. Nit just looks-wise but also weight n performance wise.

Some good quality rims which will handle the gt weight. Maybe then atleast I can use my stock tyres till they have life. And I'll save on a bunch of mods too.

Re: Changing wheel size from 18inch to 17inch C-GT

If I were you, I would stick with what Monk says. The rims are selected for a reason and changing it could have lots of after effects.. and tire options again would be a problem. Even for 17" wheels..

Re: Changing wheel size from 18inch to 17inch C-GT

Yes that's why I asked about options in 18inch alloys since the ones I see here are cheap knockoffs which many bulleteers use to make thier bike look like Harley.

I need some good quality alloy wheelset

Re: Changing wheel size from 18inch to 17inch C-GT

Parado alloy wheels...

Alloys for RE Continental GT

Hi guys...i request all fellow xbhpians to help me source alloy wheels for my GT...it is a fabulous bike, but it is a big hassle to get a puncture repaired, also since it comes with tubeless pirelli tyres, it's a pity they have tubes fitted inside...thanks in advance
Regards

Re: Changing wheel size from 18inch to 17inch C-GT

Hehehe I'm trying for the same my friend.

Re: Changing wheel size from 18inch to 17inch C-GT

But most of the wheels look cheap copies of Harley. I'm from Mumbai and there's a decent shop called ah helmets in Andheri I'll be going there to check few things out