Front tyre profile

[Sniper]

Hey all,

Im just curious to see if a claim made by a bike shop to sell me a tyre is true.

On my CBR, the front tyre is definetly a bigger profile than what it is meant to be. I can't check what it is now cause Im at work and the bikes not at home, but anyhoo. I know it is a bigger profile because I had to get a new front gaurd after the tyre kept picking up stones and using then to mash the front gaurd and put a few holes into it.

Anyway, the bike shop, who will stay un-named, said that with a bigger profile front, the bike will handle like shit. Now I think the handeling is pretty good at the moment, but will putting a smaller profile front (GPR70) make the bike handle a bit better?

Cheers

[limbimtimwim]

Anyway, the bike shop, who will stay un-named, said that with a bigger profile front, the bike will handle like shit. Now I think the handeling is pretty good at the moment, but will putting a smaller profile front (GPR70) make the bike handle a bit better?You mean, let's pretend, it has a 120/70 on the front at the moment, and the manual says it should have a 120/60 on it?

My understanding is that it should tip in better with the taller tyre.

But tyres are weird. One make 120/70 will have a 'pointier' profile than another make. And different models of tyre of the same make will also have different shapes.

I if I remember correctly the profile tells you the tyres 'tallness' in proportion to it's width.

[Sniper]

yep, as in (I'll use a cage tyre) 175 70 R13
175 is the width across the tyre
75 is the height
and R13 is the diameter.

[DEATH_INC.]

A taller tyre may tip in easier,but it'll turn faster on the smaller one.A smaller diameter will turn faster than a big one for a given lean angle.Also you're stretching the front out by raising the height with the bigger tyre.And it'll be heavier too.

[Sniper]

Thats what I wanted to hear, thanks Death

[R1madness]

Hmm. A taller tyre will not tip in quicker (gyroscopic effect). It may tip in more (further over) for the same lean angle and will definitly feel worse. The correct width and profile will definitly help. The tyre guy seems to be on to it.

[riffer]

yep, as in (I'll use a cage tyre) 175 70 R13
175 is the width across the tyre
75 is the height
and R13 is the diameter.

Don't mean to be a pedant here, but I'm pretty sure the second figure (or the profile if you wish) is a percentage of the width, not physical dimension:

i.e. 175 is the width of the tyre
70 is the height (70% x 175)
13 is the diameter of the wheel.

[XTC]

You are right Riffer. Second number is what they call the aspect ratio. Percentage of width for height.

[Holy Roller]

Talking at our club BBQ last night the guys with R6 and SV650 remarked that a higher profile tyre gave them better handling
I guess its up to individual preferences and expectations or setups that the bike has.

[Sniper]

Thanks Holy Roller. Maybe I will try the GPR70 and then based on what its like, I may make a desition from there.

Riffer, you are right mate, my mistake.

[DEATH_INC.]

Hmm. A taller tyre will not tip in quicker (gyroscopic effect). It may tip in more (further over) for the same lean angle and will definitly feel worse.
What it does is very similar to using a smaller rear , it slows the turning down so the bike resists less when you lean it giving the effect of feeling like it handles better.....

[Swoop]

Just had the same on the vfr. The fitted front tyre was wider than the reccomended size for that rim. Now have correct size and scuffing-in. Handling has lightened up a bit!

[Sniper]

I think thats what Im after swoop. The handeling on my bike does feel a bit "Heavy" so Im hoping to change might lighten it and make it a bit more flickable.

[Drew]

Once you have said correct tyre fitted and scrubbed in, try to annalyze what the bike is doing and when.
I say this because a marked improvment can be obtained by putting a wider tyre on the back of most bikes. This is not a rule! Just an observation on my experience.
But a wider back tyre, means that when leaned over, the rear end effectively raises up, thereby reducing the rake. meaning more feel. Too much though and you have a constant feeling of the front washing out, even though you make round the bend.

[Sniper]

This is the front tyre Im talking about though.

[HDTboy]

Sniper you won't be disappointed with the gpr70 in the right profile, I found myself using the front a lot more after I changed to the GPRs, to the point where I had no chickens on the front, and the rears were still evident.
The other thing you'll notice with them is just how sticky they are even from cold

[Sniper]

Thanks mate.

[TwoSeven]

ok, a 120/60 is 72mm high, the 120/70 is 84mm high (both are 120mm wide).

I used the dunlops gpr's and pirelli dragons on mine when I had it - they were both good.

[HDTboy]

They're no good on grass though, just for the record
Oh, and my front's a 110/70R17

[TwoSeven]

Thats the stock size for a mc22, what is it an avon ?

[HDTboy]

GPR-70 sp

[Stevo]

Thats the stock size for a mc22, what is it an avon ?
I am pretty sure Sniper's is a 110/70 as well which I was suspect about as the FZR has only a 100. But I said nothing at the time cos I didn't know what the CBR's recommended tyre size was. There was a definite problem, (that much was obvious), But I didn't have time to investigate as I was attempting to rebuild the 1000 pieces of Miss Sniper's bike that was scattered across the garage. :rofl:

I did note the massive difference in clearance the FZR fender had from it's tyre compared to the MC22 tho.

[Sniper]

I didn't have the front fender on when you saw it last :bleh:

[Stevo]

No, cos it was munted. When T showed me it I asked how it hapened so she sat it on the bike to show me.
Aaaaaaaaaaaah! All became clear:sherlock:

[miSTa]

I would also imagine that you would get more (marginally) tyre flex with a taller tyre that may also have an impact on the 'feel' of the front end in bends.

[Stevo]

Hey all,

Im just curious to see if a claim made by a bike shop to sell me a tyre is true.

On my CBR, the front tyre is definetly a bigger profile than what it is meant to be. I can't check what it is now cause Im at work and the bikes not at home, but anyhoo. I know it is a bigger profile because I had to get a new front gaurd after the tyre kept picking up stones and using then to mash the front gaurd and put a few holes into it.

Anyway, the bike shop, who will stay un-named, said that with a bigger profile front, the bike will handle like shit. Now I think the handeling is pretty good at the moment, but will putting a smaller profile front (GPR70) make the bike handle a bit better?

Cheers
SOLUTION: Get a bigger badder Honda for the stable.

[Sniper]

It wasn't munted? It was graniticaly modified. (IE: has a big hole in the top of it) Oh, well, I may as well at least try a new front..

(BTW: Stevo, Im up your way on Thursday night.)

[Sniper]

SOLUTION: Get a bigger badder Honda for the stable.

T won't let me spend that much.:eyepoke:

[Stevo]

It wasn't munted? It was graniticaly modified. (IE: has a big hole in the top of it) Oh, well, I may as well at least try a new front..

(BTW: Stevo, Im up your way on Thursday night.)
How funny, I gonna be down your way. I'll wave as I pass ya:lol:

[Sniper]

How funny, I gonna be down your way. I'll wave as I pass ya:lol:

Bugger, so why are you down here then?

[Stevo]

Stag do (bros). Back Fri morning maybe then possibly home again, who knows. But the wedding is down there on Sat. Got a bed?

[Sniper]

I'll be in masterton. Flatmate will be home so you can still stay at mine if you want.

[sAsLEX]

Hmm. A taller tyre will not tip in quicker (gyroscopic effect).

well maybe true at higher speeds, I noticed a huge difference going from a 60 to a 70 profile front on the NC30. It now "tips" in heaps faster and feels a little more planted through the turns, nearly fell off the thing when the tire was first put on as I threw my normal amount of body language in for a turn and was then having to pick it up before the corner.

[R1madness]

Ok now we are getting into the difference in terms of discription.
Yes it will lean over faster i agree, because the tyre is taller you need to lean it more to get the bike to the same lean angle (i am talking about the length of the arc your body travels from vertical to leant over, not lean angle here). No it will not turn in faster because of the more leaning for the same angle but it will definitly affect the way it feels. If a taller tyre front helped you try to raise the front end a little by pushing the front forks down thru the tripple clamps by 5mm (assuming they are not right down yet) or add a little preload in the front.
I am also assuming you understand that the difference between a NEW tyre and a wornout one is huge even if it is the same size and make. A worn one slows steering and makes it feel heavy.
Fiddle away man its how you find out what works. Do not be afraid to play with the knobs on your forks and shock. Have a twiddle and go for a ride. Note down what has changed in the way the bike behaves and fiddle again. Repeat until it feels great.

[Sniper]

I wish it was that easy R1madness. I can happily adjust my rear shock, but my fronts I can't. What do you mean by dropping the front forks?

[R1madness]

Ok. Have a look at the top tripple clamp. Is the top of the forks poking thru or are they flush with the top of the tripple clamp? If they are pokiing thru and you want to have a little play then you need to support the bike so the front wheel is just off the ground and loosen off the bolts that hold the forks into the tripple clamps as well as the ones that hold the handle bars to the forks. Now carefully push the forks down until they are level with the top of the tripple clamp. You may need to twist them as you push. Then tighten up everything and go for a ride. How does that feel now?
When was the last time you had your fork oil changed? You can change the whole feel of the bike by changing the fork oil viscosity. In the days before adjustable forks we used to combine different weights of oil to change the damping effect and add some washers to the spring to change spring preload. Thank god for fiddly knobs and aftermarket spring suppliers.

[Sniper]

Lol, yep, the oil was changed in both forks about 3 months ago. I put them flush with the thriple clamp. Maybe a bit of a play is in order aye.

[R1madness]

Sounds like you have it pretty well sorted actually. Is there something in particular you want your bike to be able to do better?

[Sniper]

Like I said earlier, the handeling just feels heavier compared to a CBR250RR I took for a spin a while ago.

[R1madness]

Now we are getting to it.
Do you mean heavy to turn in? Heavy to pick up after the corner? Needs a lot of pressure on the bars to keep it turned in?
All will be affected by a change in tyre brands/compounds and air pressures. By the way what tyre pressures are you running?

[sAsLEX]

. By the way what tyre pressures are you running?

I always used 32psi front and rear, on my rr with gpr70s, and this always worked good as a guide.

[TwoSeven]

You still havnt posted what tire you now have on the bike (make and size) :)

[FlyingDutchMan]

If the tyre has been squared off, it makes the handling real heavy/shit. But your tyre is pretty good - it didn't seem that bad when I was on it. The manual recommends 110/70 - R17 for the MC22.