1974 Honda CB360 - Tire / Rim size
- Thread starter tozer9
- Start date
but it will handle better with the smaller tires and the suspension will work better and you will stop quicker and it will steer easier and it will accelerate quicker
the only reason for larger than ideal tires is vanity the rest are all negatives
nice bike by the way
kudos to you for not making a hacked up mess out of it
the only reason for larger than ideal tires is vanity the rest are all negatives
nice bike by the way
kudos to you for not making a hacked up mess out of it
crazypj
Split personality, I fake being smart
Wow, I had forgotten about this, 3 yrs old.
Thought people could have done some searching and found all the relevant information by now, explanations of matching tyre size to rim width and the reasons for 'doing it right'
Just because you can fit oversize tyres on the rims it doesn't mean you should or that it handles as well as you think. From various people on DTT who have fitted wider rims and closer matched tyre sizes, handling is vastly improved.
All you have done is make bike twitchy with tyres that WILL wear out way faster than they should.
Your picture of rear tyre shows contact patch about inch and a quarter (?) wide, narrower tyre will give a wider contact patch
A picture at slightly greater angle from behind will show how much the sidewalls bulge out from rim, the bulge means you need to use higher pressure (or stiff sidewalls) to prevent tread moving 'sideways' during cornering
Thought people could have done some searching and found all the relevant information by now, explanations of matching tyre size to rim width and the reasons for 'doing it right'
Just because you can fit oversize tyres on the rims it doesn't mean you should or that it handles as well as you think. From various people on DTT who have fitted wider rims and closer matched tyre sizes, handling is vastly improved.
All you have done is make bike twitchy with tyres that WILL wear out way faster than they should.
Your picture of rear tyre shows contact patch about inch and a quarter (?) wide, narrower tyre will give a wider contact patch
A picture at slightly greater angle from behind will show how much the sidewalls bulge out from rim, the bulge means you need to use higher pressure (or stiff sidewalls) to prevent tread moving 'sideways' during cornering
Well, there certainly are a lot of opinions on changing rim and tire sizes. Having done a fair bit of "experimenting" myself, I've ended up in the conservative camp. Seems to me you can boil it all down to a few simple and really sort of common sense concepts.
Regarding the tire size vs. rim width: A lot of times you can mount the "next larger" tire width without much ill effect. It depends very greatly on the tire! How the tire behaves depends a lot on its construction and how stable it is in the rim. I think it is obvious that a tire too wide for the rim will be poorly supported. Lean it over far to one side, and the edge of the rim is not in the right spot to support the load like it would if it was matched size-wise. So the tire will distort in a way that likely will be undesirable. Add a bunch of air pressure, or change the construction of the carcass, and it might not be so noticeably. Or just take it easy and you may not even care. I think a lot of us have simply changed to a same size but different brand tire and noticed big differences in handling, so you may change to a bigger tire, and get hard to quantify results. Regardless, the tire needs to be properly supported by the correct size rim to perform well. Most tire makers spec the rim width they want, and usually very little if any margin for "adjustment".
So, ok, bigger tires with wider rims to support them. What's not to like about that? Well assuming there are no clearance issues, you can't go very far before bigger, heavier tires take a dreadful toll on handling. Unsprung weight is the bane of motorcycle handling. Bikes are already disagreeably light compared to their wheels and unsprung brake and suspension components, and with a lot of people making their bikes lighter this problem is made worse. Making the wheels even heavier won't take much to wipe out any notion of improvement from contact patch. Even worse, on the front, the greater mass reduces the natural frequency of the assembly, making the dreaded speed wobble arrive at a lower velocity.
And regarding diameters. It's more complicated than it may appear at first. A larger wheel lifts the bike, so compensation on the other end will be needed if you don't want to change the rake. Even with the rake maintained, you will increase the trail if it is a larger front diameter. These things affect handling rather noticeably, but if you don't push your bike very hard, maybe it is ok (a lot of people like choppers, which handle unbelievable bad) - it's a trade off. If you are going to fool around with diameters and you are also interested in handling, you would be well served to learn a bit of the engineering involved if you expect intended results.
Consider the manufacturers intent. They know what they are doing. It is no accident the incredible similarity of say - all street bikes of any given era. They are all nearly the same in geometry and spec for a good reason. Making big changes for the sake of appearance at the expense of performance is a bad choice for many. So keep very close to what the original maker found to work well unless you know as much as they did. They REALLY wanted you to like your new motorcycle! Building a good looking motorcycle that sucks to drive, well it SUCKS! But like I said, lots of people like choppers.
Regarding the tire size vs. rim width: A lot of times you can mount the "next larger" tire width without much ill effect. It depends very greatly on the tire! How the tire behaves depends a lot on its construction and how stable it is in the rim. I think it is obvious that a tire too wide for the rim will be poorly supported. Lean it over far to one side, and the edge of the rim is not in the right spot to support the load like it would if it was matched size-wise. So the tire will distort in a way that likely will be undesirable. Add a bunch of air pressure, or change the construction of the carcass, and it might not be so noticeably. Or just take it easy and you may not even care. I think a lot of us have simply changed to a same size but different brand tire and noticed big differences in handling, so you may change to a bigger tire, and get hard to quantify results. Regardless, the tire needs to be properly supported by the correct size rim to perform well. Most tire makers spec the rim width they want, and usually very little if any margin for "adjustment".
So, ok, bigger tires with wider rims to support them. What's not to like about that? Well assuming there are no clearance issues, you can't go very far before bigger, heavier tires take a dreadful toll on handling. Unsprung weight is the bane of motorcycle handling. Bikes are already disagreeably light compared to their wheels and unsprung brake and suspension components, and with a lot of people making their bikes lighter this problem is made worse. Making the wheels even heavier won't take much to wipe out any notion of improvement from contact patch. Even worse, on the front, the greater mass reduces the natural frequency of the assembly, making the dreaded speed wobble arrive at a lower velocity.
And regarding diameters. It's more complicated than it may appear at first. A larger wheel lifts the bike, so compensation on the other end will be needed if you don't want to change the rake. Even with the rake maintained, you will increase the trail if it is a larger front diameter. These things affect handling rather noticeably, but if you don't push your bike very hard, maybe it is ok (a lot of people like choppers, which handle unbelievable bad) - it's a trade off. If you are going to fool around with diameters and you are also interested in handling, you would be well served to learn a bit of the engineering involved if you expect intended results.
Consider the manufacturers intent. They know what they are doing. It is no accident the incredible similarity of say - all street bikes of any given era. They are all nearly the same in geometry and spec for a good reason. Making big changes for the sake of appearance at the expense of performance is a bad choice for many. So keep very close to what the original maker found to work well unless you know as much as they did. They REALLY wanted you to like your new motorcycle! Building a good looking motorcycle that sucks to drive, well it SUCKS! But like I said, lots of people like choppers.
SASO Racing
Been Around the Block
Hey. I did a LOT of research and got the well respected oppinions of a few people in this thread actually.
In addition to upgrading the rims to aluminum from steel you will save weight, look better/ wider and more aggressive, wont rust.
And most important, the handling of a wider spread of the tire for a better contact patch
Sizes: 2.15 front and rear from Mikesxs, I used the old spokes and nipples, cost wasn't bad!
This allowed a 90 in the front and 110 rear. 100 rear might have been a little better.
These wider rims spread the front and rear out very nice. I cant tell you how much better these rims feel with handling.
Sometimes with oversized tires without the wider correct rims a bike will feel wobbly, expecially if you take your hands off the bars for a second. These feel great and I can ride no hands
They look amazing too, see for yourself:
In addition to upgrading the rims to aluminum from steel you will save weight, look better/ wider and more aggressive, wont rust.
And most important, the handling of a wider spread of the tire for a better contact patch
Sizes: 2.15 front and rear from Mikesxs, I used the old spokes and nipples, cost wasn't bad!
This allowed a 90 in the front and 110 rear. 100 rear might have been a little better.
These wider rims spread the front and rear out very nice. I cant tell you how much better these rims feel with handling.
Sometimes with oversized tires without the wider correct rims a bike will feel wobbly, expecially if you take your hands off the bars for a second. These feel great and I can ride no hands
They look amazing too, see for yourself:
Attachments
SASO Racing
Been Around the Block
Also in case anyone is wondering this. And PJ you might have told me this.
2.15 is just about the largest you can go if you plan on using your stock spokes.
Everything bolted right up no problem.
2.15 is just about the largest you can go if you plan on using your stock spokes.
Everything bolted right up no problem.
