Tyre Price

https://tyretectrading.co.uk/tyres/avon-av92-cobra-chrome-200-50r17-75h-tl-rear-motorcycle-tyre/ £169

 

£235 sounds excessive, what size are your tyres? Doing detective work on your postings about a Thunderbirsd 1700 and looking online, they seem to use 200/50R17 which are £169 from the place I always use. (Plus £7.50 delivery)

The prices have gone up a lot though. My rear 150/80R16 was was £119 a year ago and it's currently £150 so a 26% increase.

 

They are a lot more expensive, but unless I'm missing something, they're £200 from TyreTec.

 

I would check your Triumph booklet mate. I think the previous owner may have put a 55 on but I believe standard is a 200/50 R17, so then the choice is yours

 

@Bucky I think @Helmut Visor and @ Brown Mouse are right about tyre sizes for your bike. I was just looking up tyre options for my bike using Triumph's recommended tyres brochure and presumed to check for you as well; none of the cruiser range use 55 profile tyres. The link to Triumph's tyre selector is

Your Triumph | For the Ride (triumphmotorcycles.co.uk)

Hope this helps

 

I just payed € 420/USD 423/GBP 355 for a complete exchange of the tyres of my Honda NT-1100. For the T120 I payed € 350/USD 353/GBP 296 two weeks ago. The Honda got Continental Road Attack 4 and the T120 Bridgestone BT-46.

 

Short answer, yes a 55 profile tyre will fit but the rolling radius (diameter) of the wheel+tyre will be bigger.

Long answer, but this will have the effect of your making your Speedo read slow because the wheel will travel further along the road for one rotation of the wheel. For example if your rear tyre is supposed to be a 200 50 17; the last number is the diameter of the wheel in inches, the first number is the tyre width in millimetres, the second is the height of the tyre/sidewall as a percentage of the width, 50% of 200 is 100mm. If you use a 55 profile tyre the height becomes 55% of 200 which is 110mm which is quite a difference.

So the saddle will be 10mm higher off the ground, and you’ll be travelling about 5-7% faster than the Speedo thinks you are, risky for your licence especially if you like to play the 10% Speedo error game when observing speed limits, you may also notice a slight reduction in acceleration, although on your beast, that’s doubtful.

The above assumes that you’re replacing a 50 profile tyre with a 55, but if you are replacing a 55 profile tyre with another 55 profile tyre you won’t notice any difference. That said the Speedo will still be reading slow because Triumph designed it to work with a lower profile tyre.

Personally I’d double check what Triumph fit as standard and go with that even if it meant the hassle of returning a tyre, especially because the 50 profile tyre will probably be a lot cheaper.

Hope that helps and you get it sorted.

 

Unless the computer uses the front wheel's ABS ring for determining speed.

EDIT: Bike in question is old enough to maybe have optional ABS? If so, possibly has another means of determining road speed. Though on another forum someone with same bike (I think) had problem with ABS warning light coming on and speedo not working, so that implies they are connected.

I make it just over 3%. The radius of 17 inch wheel is 216mm so radius with 'proper' tyre is 216mm + 100mm = 316mm. The new 55% ratio tyre would increase that to 326mm and 326/316 ≈ 1.032 or 3.2% more.

 

@brown mouse, your maths is spot on, my mental arithmetic (in my defence at one in the morning) still needs work. 3.2% error is less drastic, but the 50 profile tyre remains a lot cheaper.