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Tyre Size Question

3K views 27 replies 8 participants last post by  Donsy 
#1 ·
Hi Guys, I want to tap into a bit of knowledge from the racers/trackers here.
I've purchased a Triumph Daytona 675r and plan to track it alot next year. I may also enter a few race rounds, well i will actually.

My question is regarding tyres.
The bike comes standard with a 180 on the rear. And ive always used and liked 180's. I have ridden bikes with 190's on, but Ive never really had a chance to test a 190 properly, not on track at least.

Im doing a track weekend in Cartegena in Spain in a month and im going to purchase some tyres before i go. My question is, what are the real pros/cons between 180 vs 190.

My understanding is:
190's give a larger contact patch and allow more extreme lean angles(BTW its a 5.5inch rim and i believe most 190s are for 6 inch rims so does this increase ride height?)

190's, especially those on a 5.5inch rim, make the bike less agile, ie harder to flick from one side of the tyre to the other.

A 190 can often mean that suspension needs resetting up?

what do you guys suggest? Ive been riding for 17 years, but im fairly new to track riding. I'd like to think im a quick rider, but wouldnt we all....

From the 180's that ive used in the past, ive gone right to the edge on all of them so would i benefit from that extra 5mm on the 190?

Sorry if this has been discussed in the past. I guess it probably has.

cheers
Rich
:f4:
 
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#2 ·
On a 675, I'd stick with a 180 Rich.
Yes the steering will be affected because of ride height, but also because of that increased contact patch.
But the worst is the unspring weight, put a 180 on a scale and then a 190, not a nice result for a 675 motor or your suspension.
Just my AU$2.00

Oh yeah, then there's the price difference.
 
#3 · (Edited)
Tyres

From experience I would go with a 180 tyre to start

If you need more grip then you are are a better man than me.
I swapesd a 190 for a 180' on my 750 and felt it changed direcetion much quicker.
BUT!! With my current 312 I have no problem with the sticky Michelin Moto 2 200 section, tyres at all in Cheste.
No help, but whatever you are happy with
 
#6 ·
How can a 180/60 be the same size as a 190/55?

Diagram Line Parallel
 
#7 ·
Easy Chuck, believe me, that drawing means nothing in todays tyre construction.
Remember, 180/60 means that the sidewall is the equivalent of 60% of the usable 180mm tread pattern, and therefore, 190/55 is 55% of 190mm useable tread pattern is sidewall construction. Work that out.
And then, when you're done, look at the bow in the carcass construction, I mean tyre on rim, it will make you a believer.....
 
#8 ·
It is still a different "size"...that is the standard for measurement, not the fitment on a particular wheel.

Terms are important. 190 gives 10 mm more rubber surface, edge to edge, than a 180.
 
#10 ·
Where's the fun in that?:smoking:
 
#12 ·
Absolutely agreed, Dons.
 
#15 ·
Do you mean "Peope" as in tire manufactors? The Pirelli 180/60 has a 193mm width. Using the pic you posted, which I agree with on how to size a tire, means the tire is actually a 190 that is marketed as a 180. I believe they only market them as 180s so people know they were designed for 5.5" rims.

The big question I have on the new race tire sizes for 5.5" rims, are the width measurements taken mounted or unmounted on the rims? I assume unmounted because of the unused part of the tire on my ZX6r.
 
#17 ·
The big question I have on the new race tire sizes for 5.5" rims, are the width measurements taken mounted or unmounted on the rims? I assume unmounted because of the unused part of the tire on my ZX6r.
Make no assumptions. Tire storage practices and tire dynamics would dictate that dimensions are for properly mounted and inflated tires.
 
#16 ·
nk140, are you saying the mounted and inflated width of a Pirelli 180/60 on a 5.5 inch rim is 193mm?
 
#20 ·
Some things require common sense. Any tire will not have a uniform dimension if it is not constrained by mounting and inflating. Tires are designed for a particular rim dimension by convention. If you put a 180 section tire on a 3.5 inch rim or on a 7 (dimensions exaggerated for dramatic effect) inch rim the final dimensions will vary and some will be dangerous.
 
#21 ·
Notice that the chart gives a recommended rim dimension as well as a cold and hot inflated pressure.....

Conversely, why would a manufacturer give uncontrolled (unmounted and deflated) dimensions? Those measurements would be all over the map.
 
#23 ·
Um, the world isn't perfect.
 
#24 ·
Here is my experience with tires. I've burned through multiple sets of Dunlop Q3's on both my MV 910s Brutale and my Ducati 996. The Ducati came shod with 190/50-17 tires and the MV had 190/55-17 in the rear. The MV has a rim width 1/2 inch wider than the Ducati. I can go all the way to the edge with the MV. I put 190/55-17 on the rear of the Ducati and the profile is more round because of the narrower rim. I still have a chicken strip on the Ducati because of the profile. The bikes handle almost the same. I changed the fork angle on the Ducati to the faster position, which gives the steering geometry less trail. The Duc tends to turn in faster toward the apex now than the MV. Before the steering change the opposite was true. They are both great bikes and each has its pros and cons. For the tight canyons I love the MV... for the fast sweepers I prefer the Duc. Both are almost matched in power and handling, but the MV garners more looks when parked than the Ducati ever did.
 
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