Wheel advice: 1.85 or 2.15. What's best? Lightest?

[gavinnz]

Well if you are looking for facts you definitely came to the wrong place.

Now...tell me,... do you mean the Bucket list, Kiwibiker forums or the Internet in total!!!

The funny thing is that the intenet is full of hearesay... as opposed to facts. Telling the difference is sometimes the hardest part!

Regards
Gavin

[Farmaken]

Hi Gav, I have run a set of pilot sporty tyres in the same sizes you are looking at mounted on 2.15 front and 3.00 rear rims.( tzr 250 front and gsx 250 rear )
Not sure on weights but I do know that the rear tyre was pinched too much on a 2.5 rim
Hope this is some help

[gavinnz]

Hi Gav, I have run a set of pilot sporty tyres in the same sizes you are looking at mounted on 2.15 front and 3.00 rear rims.( tzr 250 front and gsx 250 rear )
Not sure on weights but I do know that the rear tyre was pinched too much on a 2.5 rim
Hope this is some help

Thanks for that info. Do you like the tyres?
Regards
Gavin

[Buckets4Me]

hi there we run all sorts of rims on our bikes (mainly fzr250 rs125honda and wire spoked rims with and without disks on the back)
the rs honda rims are the lightest cast rims we have (early ones may be slightly wider 2" and 2.5")
wire spokes rims as run on Chambers fzr are light and have the disks frount and back but are 2.5" and 3.5"
these are 36 hole and for some form of motard bike (cost about $400 a set. not sure where from)



my 2cents worth is the wire wheels will be a lot lighter than most cast road bike wheels
and much easier to get in the sizes you want
you will have to re spoke some rims on to the right hubs (bit of a mix and match thing)

you can find some pitures of chambers bike in the ESE thread (look under thread tools)

this is his old bike but the same wheels now in an fzr250 frame

22h/p at the wheel and a good rider could still slide both frount and back wheels at the same time in the sweeper

[RideLife]

Thanks for that info. Do you like the tyres?
Regards
Gavin

I'm a bit bias of course, but some one (like me) who has used them needs to tell you.... You will be disappointed with the Pilot Sporty for Track use. Read the reviews on here. They are not up to the task of putting you at the front of the field (given that's why your out there?).

Good luck with the project.
Racey.

[Farmaken]

I found that the Pilot Sportys worked ok but they are certainly not race tyres - good fun if you like controlled sliding though !!

[F5 Dave]

. . . . I am wondering
how much of that tyre choice was really late 1980's fashion and not sound
motorcycle engineering. After all not long before that a 110 or 120 tyre was
considered fine for the back of a big bore sports bike on the '70's.

Bearing in mind that the 70s brought us spindly frames & swing arms that could be bent by hand complete with rubber bushings. . .

. . .The wider the tyre the further away the contact patch is from the centreline of the bike. . .

But a bike corners by moving the wheels onto a section of the tyre so that transposed -it is like rolling a cone. Certainly old flexi frames can be given conniptions by modern tyres.

. . . . So what gives? What am I missing the point of?

The point of a tyre from a physics point of view if you don't think about it too much, is that the friction of a tyre against the road is on contact area so more rubber means you are spreading the load. This is good and bad. wider rubber means more area for heat to dissipate. but less pressure per sq cm.

But the above ignores shear. The rubber on the road is deflecting, deforming & biting into the tarmac as it presses against it. That really is the point of wider rubber.

Power can unseat tyres, but also cornering force.


oh sure you only have to look at a Mito to see fashion driving huge tyres on a bike that doesn't need it. But I'd be keeping your std ones & spend the money saved into rebuilding the suspension.

[Grumph]

Interesting - been there. Built a Nordwest into a roadrace single for a customer some years back. it's sitting in the collection of a well known BEARS official in ChCh now.
I used the Nordwest rear rim and as he had one, an RS250 front. That gave us from memory 3.5/4.5 rims both 17's. can't remember what tyre sizes we used but it handled very well indeed. Std Gilera rims are very heavy - at least the Norwest ones are. If you're big boring a Saturno i'd use the sizes it came on.
It's theoretically posible to overtyre a single...but much easier to undertyre it...and yes you will notice the difference. the big difference between small lightweight singles and the Gilly is torque...tyres of adequate section will make it work. Nothing worse than farting round on the edge of a narrow tyre.
The Classics run the narrow rims and tyres because they have to - given a free hand most would go wider.

Still got a couple of shim under bucket conversion kits i made up for the BMW/Rotax motors - they'd fit the Gilera too.

[koba]

oh sure you only have to look at a Mito to see fashion driving huge tyres on a bike that doesn't need it. But I'd be keeping your std ones & spend the money saved into rebuilding the suspension.

This is very good advice.



I've been along the same train of thought you are on. I know there are a few people down south who love narrow tyres over wider ones.
I have since realised it was one of those blind alley things. MOST bikes have around the right amount of rubber.

Their tracks are different to ours though, and I'd guess that unless you had some super-expensive super-sticky low volume tyre they'd be far inferior to proper sizes for 125 slicks on our tracks. (I know its not relevant to you but you asked in the bucket forum.)

For us it is mostly dictated by availability of cheap rubber so sizes reflect that.

Remember when comparing old to new that radial tyres are different to crossplies, which run on a narrower rim size for a given width of rubber.

There are two elements to separate in you analysis 'road-holding' and 'handling'.

I'd say not to go any narrower if you plan on riding it hard. If you do plan on riding it hard I wouldn't worry too much about the weight as other aspects will give a far better cost/benefit.
husaberg (username) recently posted a great article by Kevin Cameron on this, LOOK HERE.


Saturno is a cool bike, you should post up some pics.