davemosstuning

Day 3: Carcass dynamics

Have you ever sat on the tire you are buying to see if the carcass will hold your body weight?

Have you ever pushed on the tire to see how it will flex?

Have you ever pulled on the sidewalls to see how much they will deflect?

Have you ever measured the new tires circumference once it is fully inflated?

Have you ever mixed brands between front and rear tires?

Street/road tires
Are built generally for durability and therefore longevity. They are normally one compound across the entire upper surface. Tires are generally fairly robust in terms of carcass rigidity to meet those goals and pressures generally reflect that design. There are a range of pressures of course for obvious reasons: - compare at BT016 to an Avon Touring tire and it makes sense IF you feel the way the tire flexes.

Hypersport tires
Are constructed for a specific purpose and have hard carcass center and a softer outside edge of various measurements in width. That means the tire will flex one way with the hard center, then flex differently when on the side/softer compound. That creates different levels of flex and feel and as a rider you need to be prepared to experience that. Were you aware of this?

Track tires
Are built specifically for this purpose and are usually one compound across the upper surface. They come in several compound types from soft to endurance. Some have numbers, some have letters to designate the compound. All brands feature different carcass designs, so the feel from the tires will be dramatically different based on carcass rigidity, sidewall flex, pressures required etc. These tires can be DOT with sipes or slicks and therefore can offer very different levels of feel and flex based on the manufacturers carcass design.

So how many of you have spooned on a new set of tires, then gone off for a blast with no consideration for what you bought, how it feels/works and what the pressures need to be and with no consideration for geometry effects based on changed tire circumferences? #$%^&&$#^ !!!!!!!!!

Stop here and read these tire test reports and watch the videos. Everything that follows will be based on this material.

http://feelthetrack.com/testing-prog...0-tire-review/

http://feelthetrack.com/testing-prog...testing/761-2/

Tire circumference
If there was a 25mm difference in circumference just on the rear tire how would that affect the handling of the bike? Add in the difference on the front tire at 10mm, is the effect profound? Is it worth knowing this information BEFORE you take off and ride hard? If you don't know, the best result is you complain about the tires, the worst is you crash and have no idea why. In both instances you need a good slap across the back of the head or a derivitive thereof from your peers or what would be acceptable in your country! Not only did you massively increase your chances of being hurt but worse, you put others around you and on that road at risk. I'm heartily sick of this behavior because of the above. As the phrase goes "Free your mind" and start being much more serious in this area as of right now. It will make the bike handle much better and possibly save yours or anothers life.

If tire circumferences are drastically different, you can move the forks in the triple clamps/yokes to get some level of correction by raising or lowering the front end. if you are fortunate, you may be able to do the same to the rear end with shock ride height through spacers or shock adjustment.
Is there a mathematical formula that works every time? NO....... It's your bike and has to meet your needs, and the tires you put on will have a different roll profile, surface and sidewall flex so YOU have to experiment to find what you need. Yes, I know it is tedious, but trust me it is worth every second when you get to the pay back. Max grip, optimal wear. I'm just sayin'.......

Have you noticed that sipes/tread patterns on Hypersport and race DOT tires are getting smaller and never reach the edge of the tire? The design of these sipes is a critical engineering factor in controlling flex, so it is not a unique brand identifier designed by the marketing department!

Now think about wet weather riding with this sipe design - flaws? Spirited street and track riding - benefits? Brand differences - go look online!

DOT race tires have a significant amount of engineering put into this sipe design, so read up on why the sipes are the way they are. That will give you some hints as to how the tire will behave which can be matched to the carcass structure. Again, invaluable information.

Slicks offer the most amount of grip of all tires as there is no sipe pattern. If that is true, how does that impact the chassis and suspension on a track or race bike? Hint - read all the other tire tests I have posted at feelthetrack.com under product testing.......

This topic is the one I am most passionate about because the risk factor is so high especially for street/road/touring riders.

1. Feel the carcass of the tire you are buying
2. Measure the circumference when fully inflated
3. Store that data
4. Correct your chassis geometry based on the differences
5. Ride at 80% to feel the difference with that carcass
6. Find the cold or hot pressure you need
7. For track tires, that pressure is that day only
8. Stay with the same tire for a season or more!
9. If you change tires even within the same brand, start at 1