SIWA: Downshifting at 6k?

[Brettus]

Thanks for all the responses on the other thread, confirming what I'd thought for the most part but interesting to "canvas the popular opinion" so to speak.

Over time I've started to get more aggressive (complacent is likely a better substitute) with my riding, pushing a little more and I'm downshifting from 6 and sometimes 7k rpm as I'm coming up to the work traffic lights. I had an incident on my CBR125 when I locked the gearbox by downshifting too quickly. At what point does that happen on the SV? I know slipper clutches exist but I'm pretty sure I shouldn't be needing one for road use.
so,
How many revs are too many for downshifting?

The SIWA stands for: Should I Worry About.....
and I suspect this will be a series of threads, hence the prefix, which once each thread has been answered (if deemed useful) could be compiled into an FAQ style thread with the question and most popular answer in one post with a link to the thread for the full story.

[Purity14]

blip the throttle as you downshift so that you revmatch and you'll be fine :)

[jambo]

When you down-shift the revs will rise to what they would be at that road speed, in the lower gear. Sometimes the rear tyre will break traction, but we won't worry about that for now.

The trouble with this is that the engine is being mechanically turned by the rear tyre, and not driving itself using fuel/ignition, so can be spun faster than the point the rev-limiter would cut the spark.

So the highest you can down-shift without consequence is the one that leads to the revs in the next gear being lower than the rev-limiter. This will vary by gear as the difference in ratios between each is different.

Sometimes the rear tyre will slide as mentioned earlier but that has more to do with available grip than a specific rpm.

Jambo

N.B: So don't down-shift when you're next to the limiter or things might get expensive :D

[Dicky Ticker]

Why? surely roll on from 6000rpm is adequate

[-Ralph-]

There is no correct answer to this question. It depends if you blip, or feather the clutch, or just drop it. Slipper clutches are for Gorillas, us humans have managed for years without them.

Incorrect chain tension can cause the final drive to snatch at the rear tyre a break traction.

Then the other variable is road condition a weather. The other variable is the tyre. What is the available grip.

More importantly than what revs you are using (so long as they are not so high as to damage the engine), is the presence of mind to deal with a locked back wheel quickly if it happens.

Use your brakes to slow down anyway, they are designed for the job and cheaper.

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[Specialone]

My first track day when my sprint was less than 6 months old, i was coming to the end of the straight at mallory and didnt have a clue what speed i could take the next long right hander so i braked and down shifted from about 7.5k, i did / do blip but not enough, i locked the back up momentarily and had a wiggle, scared me a bit tbh as i was doing around a ton at the time.

Never did it again that day or since actually.

As others have said, high rpm downshifts are fine as long as you blip and are somewhere in the ball park for revs to match road speed for the gear your now in.

[Fallout]

Why? surely roll on from 6000rpm is adequate

Tend to agree. 6k is when the power band begins to kick in. Don't think you're really going to see any difference. Perhaps on a track you'd clock quicker lap times, but I reckon a smooth corner exit from a nice roll on from 6k would probably give better results on the road than screaming everywhere and constantly shifting.

Completely speculation btw. Just my opinion.

[unclepoo]

There`s really no need to change down at 7000rpm on an sv....change up yes, but change down a gear!! "no" With the engine characteristics of an sv they don`t need to be rev`d to get the best out of them...use the mid-range torque.

[Dicky Ticker]

Admittedly it is a long time since I rode an SV but as you are in the power band between 6-7000rpm why reduce your band by changing down and limiting the scope of your acceleration by having to do another gear change up once you have hit the limiter.
If we are talking road riding,which I presume we are, if the overtake is that critical you are seriously limiting your options by changing down.
A lot of noise and wasted fuel for very little gain and the possibility of a lock up or wheel spin to boot????????

[Runako]

These V Twins seem robust enough to handle a high RPM downshift. There is no way it should be getting anywhere near the limit in the scenario you describe. Otherwise there would be people diving to get out of the way and a distinct smell of burning rubber!

If the downshift is to aid stopping (which is my interpretation of your post), then blip as has been said above. Also, agree with the comment that if you're already at the red line, slow down before downshifting. Pridmore teaches the feathering the clutch downshift method which is more relaxed but obviously slower engine braking.

[Brettus]

I think I've not explained myself clearly, I'm not meaning about power band or for best take off etc, I'm just coming to a stop or slowing for a corner and I wanted to make sure that at 7500rpm or something it isn't going to lock the gearbox. I've had the rear wheel break traction and that's just acceptable behaviour. Gives me feedback on the conditions and I adjust my riding. It's just the clutch locking up that concerns me here.

Thanks for all the replies BTW, lots more info than I expected. Interesting to get the opinions from you all.

[-Ralph-]

No 7500 rpm isnt going to lock the back wheel under normal circumstances, but see my post above, that is subject to many variables, and therefore what are 'normal circumstances'?

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[johnnyrod]

There aren't many bikes where you would expect to lock the gearbox up just by some ham-fisted shifting, worst case would be a false neutral or it just not shifting. On the SV however with the alternator rotor outside of the bearing, I believe there have been a few cases of the crank giving up due to a lot of harsh gearchanges (engine speeds belting up and down). Sure I read it here somewhere (Sarah Jordan?) but can't remember for the life of me.

[Biker Biggles]

I reckon 6-7000 rpm it a perfectly good number to enter a corner so no need to change down on an sv.As for stopping,again there is plenty of engine braking at those revs so no need to upset the balance by overdoing it.

[Dicky Ticker]

Sorry matey misconstrude your OP. Like Ralph says brakes are cheaper than mechanicals and a combination of both is the answer for hard sure footed braking rather than just depending on dropping a gear risking a lock up in wet or slippery conditions.
I always look at self preservation being primary over what may appear as "Sporty" riding styles,after all what do you really gain by just depending on engine braking.

[Specialone]

I think I've not explained myself clearly, I'm not meaning about power band or for best take off etc, I'm just coming to a stop or slowing for a corner and I wanted to make sure that at 7500rpm or something it isn't going to lock the gearbox. I've had the rear wheel break traction and that's just acceptable behaviour. Gives me feedback on the conditions and I adjust my riding. It's just the clutch locking up that concerns me here.

Thanks for all the replies BTW, lots more info than I expected. Interesting to get the opinions from you all.

I understood exactly what you meant mate, hence my version doing similar :)