21 Jul 2008

Does the width of rear tyre affect stability of motorcycle?

That's my question to all great automobile/mechanical engineers out there!

The question popped up in my mind after watching the Yamaha R15 - the bike with stunning looks and a thin rear tyre 😡 .

Does it affect the stability of the mobike at higher speeds?
raj87verma88

raj87verma88

Branch Unspecified
21 Jul 2008
Frankly speaking Biggie, the R 15 is a joke. It would have been acceptable if the price range had been around Rs. 50,000 to 60,000 but a price tag of over 1,00,000 is too much to digest. If the bike had been a 250 cc then it would have been OK but for a 150 cc. Now coming to the point i.e. tyre. Its a pencil tyre. Yes, the size of the tire does effect the performance. The World Wide Web has forums and sites full of debates on this subject. I am posting some links for your reference.
Front Tire Skinny vs Fat tire - TWT Forums
Mazda6Tech - Are Wider Tires Better?
What's the largest size tire I can fit in my Xterra? - Automotive Forums .com Car Chat
Will post more later.
21 Jul 2008
Hey, thanks patty! You are no doubt well informed about bikes. Thanks for the links. Looks like there' lot to read!
just2rock

just2rock

Branch Unspecified
24 Jul 2008
Yes thats all true,patty .The bike looks awsome..crazy bike look will attract all and so will they pay also,as you seen in Karisma.But yes those who will think on the design specifications will definately stop before
gohm

gohm

Branch Unspecified
24 Jul 2008
Yes, the thinner the tire the smaller the possible contact patch. This leads to a less stabile tire that also cannot put power down to the pavement effectively. Conversely though, it can turn in quicker so improved handling.
sonasathish

sonasathish

Branch Unspecified
26 Jul 2008
i don know what you guys are trying to explain! Do you think that the engineers who designed this bike never had a thought about your point! Sounds crazy
Ashraf HZ

Ashraf HZ

Communications
26 Jul 2008
Don't forget having a thinner profile decreases the drag coefficient too!

I think so, anyway 😉
raj87verma88

raj87verma88

Branch Unspecified
26 Jul 2008
sonasathish
i don know what you guys are trying to explain! Do you think that the engineers who designed this bike never had a thought about your point! Sounds crazy
The simple truth is that a fatter tyre will provided better stability and balance and a thinner tyre better acceleration and mileage, but the tyre used in the motorcycles available in India are too thin. It is as if the companies are more concerned about their profits than anything else. And now tell me, if the thinner tyre had the same level of stability as a fat one, won't they put it on a superbike rather than those huge 200mm tyres.
I will take an example of Hero Honda Karizma, the first generation Karizma was 225cc and had the best acceleration among all bikes in India. The next generation Krizma R had the same engine but an even quickr acceleration. There must have been modifications in the engine but the thing that is to be noted is that the tyre was now thinner than the previos version's. Speed thrills and that is why these bikes are making business and also give decent mileage. Frankly speaking the companies are more concerned about their profit, sales than the safety of the riders.
A good example of a bike that had a mindblowing acceleration, good top speed, solid handling and had a not a very big tyre but a decent size is the RD series from Yamaha. RD 350 was availble here but was later banned as it was a 2 stroke.

ash
Don't forget having a thinner profile decreases the drag coefficient too!

I think so, anyway 😉
I think it should
26 Jul 2008
sonasathish
i don know what you guys are trying to explain! Do you think that the engineers who designed this bike never had a thought about your point! Sounds crazy
Yes, they must have thought of it. But you see, understanding why they did it and what they missed - could lead to new ideas & development.
gohm

gohm

Branch Unspecified
26 Jul 2008
Yep, it is a marketable product designed to fit a niche of the manufacture and be profitable. Hence there is always room for improvement and customization to taste or usage.
Mayur Pathak

Mayur Pathak

Branch Unspecified
28 Jul 2008
Guys, do you remember Naoya Kaneko's (Kawasaki) interview? He said they first decide the size of tyres before they design a bike.

Fatter tyre is used when you have a bigger engine, since you need more stability. Otherwise the vehicle will lose ground contact. Thinner tyres, however doesn't allow the bike to cruise at higher speed too much. Its difficult to turn the bike at a high speed with thinner tyres. But they are good for off the road biking, unlike SUV's where thicker tyres are used when the vehicles have to go off the road
raj87verma88

raj87verma88

Branch Unspecified
28 Jul 2008
mayurpathak
Guys, do you remember Naoya Kaneko's (Kawasaki) interview? He said they first decide the size of tyres before they design a bike.

Fatter tyre is used when you have a bigger engine, since you need more stability. Otherwise the vehicle will lose ground contact. Thinner tyres, however doesn't allow the bike to cruise at higher speed too much. Its difficult to turn the bike at a high speed with thinner tyres. But they are good for off the road biking, unlike SUV's where thicker tyres are used when the vehicles have to go off the road
You can modify your bike later. I have a Royal Enfield which comes with a 130mm tyre, I got a 160mm fitted on it. The engine feels no load, it is running as smoothly as before and there is no sufficient dip in mileage.
I agree with what Mr. Kaneko said, also he his far more experienced but we should remember that for the race track you have to be accurate. You can not have a slightly thin or slightly thick tyre there. But on road you can modify.
gohm

gohm

Branch Unspecified
28 Jul 2008
Actually it is easier to turn a bike with thinner tires at high speed. Less friction and mass to hinder the re-direction of the gyroscopic forces that cause the bike to lean.
R-series

R-series

Branch Unspecified
24 Sep 2008
raj87verma88
The simple truth is that a fatter tyre will provided better stability and balance and a thinner tyre better acceleration and mileage, but the tyre used in the motorcycles available in India are too thin. It is as if the companies are more concerned about their profits than anything else. And now tell me, if the thinner tyre had the same level of stability as a fat one, won't they put it on a superbike rather than those huge 200mm tyres.
I will take an example of Hero Honda Karizma, the first generation Karizma was 225cc and had the best acceleration among all bikes in India. The next generation Krizma R had the same engine but an even quickr acceleration. There must have been modifications in the engine but the thing that is to be noted is that the tyre was now thinner than the previos version's. Speed thrills and that is why these bikes are making business and also give decent mileage. Frankly speaking the companies are more concerned about their profit, sales than the safety of the riders.
A good example of a bike that had a mindblowing acceleration, good top speed, solid handling and had a not a very big tyre but a decent size is the RD series from Yamaha. RD 350 was availble here but was later banned as it was a 2 stroke.


I think it should
is that the maximum u knew about bikes.. tyre size depends on more than just providing stability. size of the bike also deterimes which tyre suits it better. big(wider bikes) need wider tyres to disrtibute the whole weight of the bike on the road equally so tha one point is not more pressurized compare to the other. the tyres on the R15 are the best that can be given. Karizma R was never faster than the Karizma. I had the old one and it always beat the R in a drag. not to mention the R15 has soft compound rubber from MRF which gives then better grip. wider tyres do not even determin the lean angle. since the angle purley depends upon tyre profile. a 200mm tyre doesnot necessarily provide better lean. The V-rod has a 200mm rear but still doesnt bend as much as the M1 with a 200 mm size..just because of its different profile. And talking about drag cofficient..its almost negligible compared to the total drag of the bike..so engg rarely take that under consideration and that too only for front tyres not rear. if u doubt why superbikes use up much fuell..its only because of the power. 180+bhp doesnt come for free..and to transmit that power from the engine to the road to move forward u need a larger contact area for proper weight distibution.

please revert back for any doubts...i havent done training at MRF for nothing. Im all geared up😀
R-series

R-series

Branch Unspecified
24 Sep 2008
gohm
Actually it is easier to turn a bike with thinner tires at high speed. Less friction and mass to hinder the re-direction of the gyroscopic forces that cause the bike to lean.
the handling of the bike depends upon the wheelbase, rake and trail. Motogp bikes have all these adjustable to change the handling of the bike according to different circuits. tyres do affect handling..but thats the last thing on the list that needs to be changed
raj87verma88

raj87verma88

Branch Unspecified
24 Sep 2008
@ R-series: First of all, Welcome to CE. This is a discussion going on where everyone is invited to present his knowledge. If someone has more knowledge then he/she can correct, modify or add on someone's else's answer. But as you would have noticed that people here are polite and do not demean on degrade someone else. The way you have started both your posts....it seemed to me you are more interested in picking up a fight then anything else. Anyway, thank you for adding on to our knowledge.
P.S. Introduce yourself in the CE Introductions section.
dustom_99

dustom_99

Branch Unspecified
24 Sep 2008
well..i joind this site cuz i thgt its name ws crazy engineers..i cudnt find an engineering reply to the question being askd..cmmon guyz ..lets screw manufacturers n thr profit making spree..well,,as far as tyre width goes from design point of view,,it largly depends upon type of vehicle and xpected traction it shud have,,for xample in case of indian bikes..lets say karizma,top wach is about 125/130...may be a lil more..simulation tools..(wudnt mention the name) r used to see wht sort of grip levels will be generated by standard available rubber(data taken from tyre manufacturers)and wht process of valcunisation and additives will be needed ..okie lets cutda crap..

as we all know..grip as we call it is actually transverse frictional force..in this case..limiting friction...90degrees to direction of travel..n trust me u don want ur tyres moving in tht direction whn ur on top speed.

simple school formulae..MUx R..=frictional force..
MU depends upon surface of road n also surface of rubber being used in tyre.

r is simply reaction..

now one would ask ..for bout fat n slim tyre provided both r made from same rubber..MU wud be same...yes it wud be same..
r is simply the component being returned of the projected weight...so it wud be same aswell..both for fat n thin tyre(is overall weight is same)
now some wud think but a fat tyre offers more are of contact hence more friction....absolutely rubbish..
frictional force does not depend upon area of contact...all mechanical engineers wud hv derived this shit in thr very first yr..ofcrse i kno u wud forgt this..

but hey in case of bike's stability or othr vehicle's stability r we actually talking about total frictional force..?
..vehicle is stable until the rubber or the road surface reaches its shear stress limit(ths y u slide so soon on loose gravel or mud)cuz practically its already on its shear stress limit..

althought the total firctional force is same for any tyre u use...weight per unit area in contact is very less for a fat tyre...and so the rubber in every sq cm of tyre surface has less burden and reaches its shear stress limit due to sliding limiting friction later....

now u kno haan...
oohh by day way..
i make krizma...workin at herohonda..!!
gohm

gohm

Branch Unspecified
04 Nov 2008
True, however turn-in is also dependant on tire size as well as many other factors. You can verify this by changing tire size on your bike (which I've done on many of my street and race bike) and easily note the effect on handling. Both caused by the size and mass change. That is why drag bikes use very large tires (maximum contact for usage of large torque/hp applications in a stable straight line) and road racing bikes have smaller tires designed for successful application of both speed and cornering ability. if I put drag tires on my track bike I'd be lucky to safely make a circuit around a track at anything but a very slow pace.

R-series
the handling of the bike depends upon the wheelbase, rake and trail. Motogp bikes have all these adjustable to change the handling of the bike according to different circuits. tyres do affect handling..but thats the last thing on the list that needs to be changed
superman734

superman734

Branch Unspecified
30 Dec 2008
You also need to remember that the way motorcycles turn when racing is totally different than when opperating under normal conditions. Since the gyroscopic force is so great when moving at very high speeds, it would be very difficult to simply lean the bike over into the corner. Instead, riders must counter-steer (pull on the handle bar opposite of the intended direction of travel, which forces the bike over on its side). This means that much of the force that is going towards changing direction is actually coming from the rear tire. How fast the bike can lean into a corner if primarily determined by the design of the front tire (unless you have a huge tire in back like for drag-racing)
Frankly, everything about a bike affects the stability, not just the tires (although it is a factor). Obviously, if you put the tires from a sport bike on a harley, the harley will still handle like a pig because it is a heavy sled with a poor frame design.
Here is a thing on counter-steering:
YouTube - Slow-speed countersteering
gohm

gohm

Branch Unspecified
31 Dec 2008
That is actually incorrect. Motorcycles always turn by counter-steering causing the gyroscopic forces to lean the bike at anything over 5-10mph. At 5-10mph roughly you are going slow enough to steer by turning like a bicycle. The countersteering is so light and intuitive to most riders they do not realize it. Although: tires, frame (length, rake, trail) & suspension play factors into turn-in speed; the largest factor is the rider. that is why those of us that race are able to take turns faster than a casual rider, even on the same bike. Check out this link where Popular Mechanics build a non steering bike which then could not be turned. the AMA has also bdone tests and education about this as well.

https://www.popularmechanics.com/automotive/new_cars/1268501.html
dhruvpandit

dhruvpandit

Branch Unspecified
05 Feb 2009
i want to set a 200 mm Tyre in my thunderbird, dose any one having info that where can i get it? addresses from mumbai is most preferable.

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