Tyre size question

[CookMySock]

The other possible problem is that you will run off the edge of the tyre at higher lean angles. That really is *GULP*

Thats outside my skill level anyways..

Looks like I might take the bike off the road and get the forks serviced. By the time I get it back together again I'll just get the proper tyres. Not happy, but oh well.

Many thanks folks.
Steve

[xwhatsit]

the tip in will be determined by the profile (curvature) of the tyre. Theory says that if you put a narrower tyre on, then the curve across the tread will be flattened. Which should slow the tip in. Go figure....
The other possible problem is that you will run off the edge of the tyre at higher lean angles. That really is *GULP*

I think you've got it backwards. Narrower tyre (unless we're talking about the bizarre things I've seen fitted to Super Cubs and GX125s) means a steeper curvature -- it has the same amount of maximum lean/angle, but it has all that angle within a narrow width, so it's steeper.

[cowboyz]

I swap out 180/190 all the time. My last 5-6 tyres have been ex race tyres and paying between $20-$50 per tyre and getting 7-8000km out of them makes sense to me. Certainly beats paying $220-$300/tyre for 10,000km

narrow tyre = flatter profile. Which equates to less rubber on the road at lean.
Wider tyre = steeper profile with which actually equates to more rubber on the road at lean.
In saying that I have started having "commuting" tyres and "fun" tyres. My commuting tyres have massive ammount of tread in the centre and nothing on the outside (basically fucked racing tyres)
my "fun" tyres are in pretty good nick all over. There are deals out there.
in saying all that I would probably be tempted to go 150 if it is cheap enough for commuting but would be wary of going for a blast on one.

[CookMySock]

I would probably be tempted to go 150 if it is cheap enough for commuting but would be wary of going for a blast on one.

Ok this is on a 650, and the worn tyre has a full 1cm of strip on it.. I am thinking my ability is still well inside the 150 tyre, even in blast mode.

Many thanks cowboyz.
Steve

[Sully60]

narrow tyre = flatter profile. Which equates to less rubber on the road at lean.
Wider tyre = steeper profile with which actually equates to more rubber on the road at lean.

That's a bit too simplistic. By having a tyre that is too wide for the rim you to effective get a higher crown but you also run out of tread very quickly at large angles of lean and have unpredicable traction. This is characterised by a large chicken strip that you just never use. Dangerous practice IMHO. Not so much of a big deal with the current range of 180/190 tyres on the wide rims but with narrow tyres the effect can be greater.

Too narrow tyre can create the same issues (without the chicken strip) but the traction at the limit is far more predictable.

DB the 150/70 tyre will be of quite different construction. Generally (if I remember correctly) tyres that use this size a usually crossply construction whereas the 160/60's a radials.

While I'm all about trying different stuff out with tyre sizes I've never mixed radials and crossplys and radials and all the tyre manufacturers literature strongly discourage this.

But it's up to you as it's your safety at stake here.

Hope this helps.

[AllanB]

Rear 160/70/17 - fuggered - showing canvas

Hopefully this is the result of a burnout.

If not you have plummeted in the respect metre.

I've just replaced a rear that was just down to the moulded low tread indicators - when I point a finger on either hand on the inside and outside of the tyre you realise that on a modern tyre there is very little left at the end of a tyre life. Going beyond this is frankly dangerous. Even pissing around town at 50km.

In addition

FFS its the middle of winter - if you ever need good tyres its smack in the middle of winter!

The bottom line here is that if you are tight on $ (blame Helen) then the $100 150 is got to be a shit load better than the bald farked 160 you presently have, and a lot better value than a $200 fine for not having the bike up to WOF standards.

[CookMySock]

That's a bit too simplistic. By having a tyre that is too wide for the rim you to effective get a higher crown but you also run out of tread very quickly at large angles of lean and have unpredicable traction. This is characterised by a large chicken strip that you just never use. Dangerous practice IMHO. Not so much of a big deal with the current range of 180/190 tyres on the wide rims but with narrow tyres the effect can be greater.

Hi Craig, thats curious. I feel the bike does not have access to this chicken strip also, but attributed it to my inexperience. It gets jittery as fuck over certain levels of lean and tips in and darts about real bloody quick. Quite un-funny. It also seems to have a really low profile front tyre which I assumed didnt help. Really looking forward to getting them off the bike and replacing with some pilots.

DB the 150/70 tyre will be of quite different construction. Generally (if I remember correctly) tyres that use this size a usually crossply construction whereas the 160/60's a radials.

Joo reckon itsa crossply ? Its a conti road attack... I would be shocked to discover its a crossply tyre..


DB

[MSTRS:Me]

I think you've got it backwards. Narrower tyre (unless we're talking about the bizarre things I've seen fitted to Super Cubs and GX125s) means a steeper curvature -- it has the same amount of maximum lean/angle, but it has all that angle within a narrow width, so it's steeper.

Nope I haven't. Put a tyre on a wider rim than it is designed for means that the tyre bead is pushed further out to contact the rim.
A little demo for you...hold your hands up in front of you, position your wrists about 6" apart, now curve your fingers in until the tips are touching (you create a little arch with them), now keeping your fingertips touching move your wrists apart. What happens to the curvature of the arch?
Conversely, when fitting a wider than recommended tyre, you would move your wrists closer...if you assume your knuckles are the tyre edge, see how the angle steepens? Meaning that you will never use all the tyre when leant as far as poss. And one could also assume that tip in would be vicious.

[Sully60]

Hi Craig, thats curious. I feel the bike does not have access to this chicken strip also, but attributed it to my inexperience. It gets jittery as fuck over certain levels of lean and tips in and darts about real bloody quick. Quite un-funny. It also seems to have a really low profile front tyre which I assumed didnt help. Really looking forward to getting them off the bike and replacing with some pilots.

Joo reckon itsa crossply ? Its a conti road attack... I would be shocked to discover its a crossply tyre..


DB

Yeah I forgot you were talking about a Road Attack you're right this would be a radial, but check anyway. Same rules apply.

Sometimes even the tyres fitted by the manufacturer are slightly too big for their rims, the SV uses a 160 on a 4.5" rim but there's always a small part on the edge of the tyre that never gets used even on the track.

I doubt the profile of the tyre would not contribute to the jitteriness (sp) that your are experiencing, in my opinion this would be caused more by a combination of the construction of the tyres and the suspension settings, Robert Taylor would be the man to talk to about this though.

[CookMySock]

Hopefully this is the result of a burnout. If not you have plummeted in the respect metre.

No, its a result of it being my first learner road bike, and nana riding BEHIND two other learners for 2-3000kms EACH. Hows my respect meter looking now ?

I've just replaced a rear that was just down to the moulded low tread indicators - when I point a finger on either hand on the inside and outside of the tyre you realise that on a modern tyre there is very little left at the end of a tyre life. Going beyond this is frankly dangerous. Even pissing around town at 50km.

Not following you here. Can you post a pic of this ?

FFS its the middle of winter - if you ever need good tyres its smack in the middle of winter!

ah yeah I guess. I just didn't want my new pilots flatted off just in time for summer.. sigh..

The bottom line here is that if you are tight on $ (blame Helen) then the $100 150 is got to be a shit load better than the bald farked 160 you presently have, and a lot better value than a $200 fine for not having the bike up to WOF standards.

Yup. I like this answer.

Thank you Allan.

DB

[cowboyz]

That's a bit too simplistic. By having a tyre that is too wide for the rim you to effective get a higher crown but you also run out of tread very quickly at large angles of lean and have unpredicable traction. This is characterised by a large chicken strip that you just never use. Dangerous practice IMHO. Not so much of a big deal with the current range of 180/190 tyres on the wide rims but with narrow tyres the effect can be greater.

Too narrow tyre can create the same issues (without the chicken strip) but the traction at the limit is far more predictable.

of course, both the above replys are technically correct. I am not going to argue against them BUT.......

There is a "what you are using it for" train of thought too.

Attached is my commuting tyre. Notice how it is completely fucked? Also notice how the profile doesnt actually matter and how much I dont care about the lean angle available on the tyre because it never gets a lean on it. (shown by the 4 inch chicken strips)

Chewing out the middle of a $300 tyre is not fun on the bike or the wallet.

As for the tread pattern being unpredictable at lean. There are 2 reasons for tread. 1. to get rid of water. 2 to generate heat. If if it not raining then the first is negated. If you are not being a rossi-wannabe then the second is moot.

[cowboyz]

it the other interest of fairness. this is my fun tyre which is done and being tossed.

[CookMySock]

There is a "what you are using it for" train of thought too. [....] Chewing out the middle of a $300 tyre is not fun on the bike or the wallet.

I just want to ride it around over the winter. Too many wet patches, leaves on the road, and other things that spook learners badly to be laying it over hard. This winter is time to consolidate for me. So yes, why flatten off a nice new pilot, just in time for summer.. The winter game is already over, why ruin the summer game also..

In a way, the new $200 shinko makes sense, coz I will still have it next winter.. haha, and probably the winter after..

DB

[Sully60]

As for the tread pattern being unpredictable at lean. There are 2 reasons for tread. 1. to get rid of water. 2 to generate heat. If if it not raining then the first is negated. If you are not being a rossi-wannabe then the second is moot.

You have misinterpreted what I have said. When I refer to the tread I'm talking about the part of the tyre that's on the road as opposed to the sidewall, same applies to slicks.

It has nothing to do with tread pattern, the reasons above are absolutley correct. What I'm saying is the way the tyre profile is changed by fitting it to a narrow rim then the the outside part of the tread is too close to being vertical.
This creates a situation where traction is unpredictable when you get close to the side of the tyre. Yes this is outside the scope of most road riders in normal situations but I for one like to know that if I need it it's there.
Ever gone into a corner a bit fast and used more lean than normal? This is when you need traction.

[Drew]

The 150/70 should be very close in height to the 160/60.

The bike may infact tip in slower as a result of changing to the 150. Basically cos when you steer the wheels out from under you, the rear tyre is fuck all wider than the front and wont accentuate the rate of change as much.

If you are having the bike feel jittery, I would suggest more spring pre-load on the forks, and less rebound damping at the back. WARNING, I may misunderstand what you mean by "jittery", and my advice could make things worse if it's a stability issue.