Raising the tail unit? Why?

The tail unit on my bike see's me sitting higher than I would be on a "normal" SV. I'm sitting on the bike rather than sitting "in" the bike.

Now I'd like to know the thinking about this because I've found two major drawbacks from this already.

1) The bike wheelies buch more readily now due to the higher centre of gravity
making it harder to get off the line without it rising up
2) I can't brake anywhere near as hard as I could when riding last years bike which saw me in the "correct" position, for the same reasons. The bike wants to stoppie much more readily. I nearly went over the bars on the brakes last race meeting.

So whats the thinking? I'm ready to drop the seat back to its standard position (or even lower) and lower the bars to get the same riding position. That'll allow me to brake as hard as I did last fear without fear of going over the front, and alllow me to get off the line without fear of flipping it.

... and compared to some bikes my seat is still low! There were other bikes that had the seat 4" higher than mine.

Discuss.

C

Drop it back down, seems like win win, what's the advantage of being higher, visability so you can see the peeps in front you have to overtake?, well you will be in the lead any how, so know need to worry about that, lol.

We found the stock seating height the best in terms of weight balance on the SV when racing. Sitting the rider up in the air moves all the weight forwards which under braking can transfer too much weight forwards and thus raising the chances of loosing the front end mid turn in. The SV also prefers an even weight bias over the rear of the bike to aid rear end grip and mid corner feel, hence why we leave our batteries under the seat which is the most neutral position.

If someone gave you 4kg of lead you would never stick it up front to one side!.

i think its personal preference. im riding with a fireblade seat unit. when braking and cornering i just move my backside to the back of seat to stop the front end from loading up. as for race starts i put my weight (all 10 1/2 of me) on the tank doesnt really wheelie. a surppose the added bonus is it doesnt make me feel crampt when ridng being 6ft.

must have some power carl if yours is wheeling that much or it might be them cams you bought from jhs .... lol yours is a fair bit lower than mine.

brent

With respect, and not trying to be funny or big headed I was pushing a bit harder than you. I'm also a lot bigger than you I'm going off the line at 10,000 rpm all the way through 1st and second and braking to the point where the front wheel is locking (or the bike is lifting the rear). Yours was one of the bikes I was talking about with the higher seat that mine. Id imagine I'd find it even worse on your bike.

C

But surely more wait on the bike will keep the wheel down.

Depends on where that weight is. If the bike is trying to accelerate forwards and I'm heavy, high on the top and holding on its going to want to pivot around the heavy mass. So being high and heavy is a disadvantage I'm holding the top of the bike back being heavy. the bottom of the bike is free to move so the bike lifts, unless I lean really really far forwards. Which is restricted to being sat in the seat with my arms on the bars.

Without getting too technical its thrust vectoring. If you throw two hammers with the same handles but different weight heads, the one with the heavier head is going to fly with the handle rotating around the head more. The lighter headed hammer handle will be less affected by the weight of the head. Well in bike terms, the bike is the hammer shaft and you and me are the two different hammer heads. Apply the same acceleration force from the rear tyre and the bottom of the bike moves the top part of the bike but on my bike there's an extra 7 stones holding it back.

The lower I get my heavy weight the less effect it has as I'm closer to the line of acceleration. So me being heavy and lower has the same effect as someone lighter being higher.

It works in a similar way when breaking. My heavy weight, high up, is harder to slow down as the heavy bit (me) wants to keep going and this pivots the bike. As I drop down into the bike, the centre of gravity lowers and so you can brake harder without fear of flipping. eventually you get too low and the front wheel will lock as the CofG starts to push the front tyre. This is calculated for most road bikes and the CofG is set where the standard seat position is.

Overall the lower the rider the better he can accelerate and break as the closer to the centre of gravity his weight is.

Does that make sense?



C

[ophic]

Originally Posted by Berlin

Does that make sense?

you want to turn your race SV into a low rider custom chopper? perfect sense

Originally Posted by Berlin

Depends on where that weight is. If the bike is trying to accelerate forwards and I'm heavy, high on the top and holding on its going to want to pivot around the heavy mass. So being high and heavy is a disadvantage I'm holding the top of the bike back being heavy. the bottom of the bike is free to move so the bike lifts, unless I lean really really far forwards. Which is restricted to being sat in the seat with my arms on the bars.

Without getting too technical its thrust vectoring. If you throw two hammers with the same handles but different weight heads, the one with the heavier head is going to fly with the handle rotating around the head more. The lighter headed hammer handle will be less affected by the weight of the head. Well in bike terms, the bike is the hammer shaft and you and me are the two different hammer heads. Apply the same acceleration force from the rear tyre and the bottom of the bike moves the top part of the bike but on my bike there's an extra 7 stones holding it back.

The lower I get my heavy weight the less effect it has as I'm closer to the line of acceleration. So me being heavy and lower has the same effect as someone lighter being higher.

It works in a similar way when breaking. My heavy weight, high up, is harder to slow down as the heavy bit (me) wants to keep going and this pivots the bike. As I drop down into the bike, the centre of gravity lowers and so you can brake harder without fear of flipping. eventually you get too low and the front wheel will lock as the CofG starts to push the front tyre. This is calculated for most road bikes and the CofG is set where the standard seat position is.

Overall the lower the rider the better he can accelerate and break as the closer to the centre of gravity his weight is.

Does that make sense?



C

yes a kind of get your drift. hopefully we may get more replys to find out why the seat heights get raised.

[yorkie_chris]

Originally Posted by Berlin

eventually you get too low and the front wheel will lock as the CofG starts to push the front tyre. This is calculated for most road bikes and the CofG is set where the standard seat position is.

Overall the lower the rider the better he can accelerate and break as the closer to the centre of gravity his weight is.

Does that make sense?



C

While I see what you're saying this bit is flawed, the more reaction force going on at the front tyre, the more grip you have, simply F = uR

What is really significant is the height of CoG affects the leverage an acceleration (caused by a force at ground level) has on the bike.

It doesn't matter where the rider is in this system, rider is just ballast, simply where the overall CoG is is what matters.