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[jotjotde]

After going through 2 sets of Michelin Power 6 which worked totally satisfyingly for me, I decided to test the Dunlop Sportsmart Mk4.

The Dunlop was hyped a lot this year, so I wanted to see if all this was true.

My first impression was that the bike went into corners much more willingly than any other tire I rode so far. That felt unstable and was a bit unsettling in the beginning.
More important though was the fact that the TC lights nearly constantly flashed while cornering at considerable lower acceleration than with the Michelin.
Now after 2,000 km I cannot report that was just the new tires needed to be broken in. Flashing is still happening, so I wonder what is going on.

I discussed this with several bikers, user @most recommened to lower the tire pressure. But he also suggested that the early onset of the TC might be connected to the geometry being different compared e.g. to the Michelin.

[Grauteufel]

There is probably something in that, Michelins always seem a lot rounder, the Dunlop looks very peaked.

[Fred]

I used to run used Dunlop KR364 (racing intermediates) on the road back in the 90s. I can't find a good photo, but they were shaped like a Toblerone!

[Specter]

what pressure are you running them at?    sounds like your tires are just starting to give way a bit and the tc is seeing this and not liking it.  how does it FEEL to you, especially with an electric you can hear a lot more of the grip as well.  possibly turn the tc down a notch?

the weather is getting colder out too, tires are not going to be as grippy either, will take more energy to keep them 'warm' on the road etc etc but im sure you know that.  you can try to take the pressue down a bit, see how they feel, make sure they are not getting squirrely.  Too low can also be an issue, in turns they can get kind of wiggly if the pressure is too low.  ive done that on my bike, got off the track and forgot to put the psi back to road numbers, first lean in at speed it's like ooh boy... shit, forgot to air up the tires!!  sometimes it'd feel like she just didn't want to fully commit to the turn, other times it dove right in and was like, whoa..easy there..    lower pressure will give you grip but you have to have the energy in the tires for it to work properly, and NO, road riding is not putting enough energy into the tire to keep it running right unless you are far exceeding the speed limit .. they'll dive in but feel like they want to move around a bit.  higher psi and it'll slide, or you'll run wide, thats not good either.

road ill run the back at 34  front 35 to hold the weight a bit better on harder stops.  track ill run 28 in back 29.5 up front
i like the Contenental Road Attack 2 Street.  they are good for the track and the street, and best thing you CAN race them and don't HAAVE to have tire warmers on them.  although they say you can go w/o warmers id highly recommend a warm up lap or two before you light them up.

aaron

[Anav]

I find the TC control for regen very sensitive and always have issues when replacing tires for the first 500 - 1000 mi, the bike is a ribelle RS.

 I install Dunlop Mutants which have a very aggresive profile, esp for the rears.  My guess is that the peaky profile causes the rear to roll slightly less than what the computer expects when compared to the front for the OEM tires.  This offset over the preset parameters confuses the computer and causes the TC issues.  I have done several tire changes (3 with mutants) and the issue occures, but fades progressively and goes away after a while (that seems like forever ~ 1000).  Lowering pressure in the rear seems to help as a temporary measure.  I also found that when the computer gets "confused" I have to stop and reebot to stop the issue getting increasilngly worse (basically no regen).

I think our bikes are particularly sensitive because they have to control TC both when acceleratin AND when decelerating (regen). It's all about the relative wheel rotation speed between rear and front, but in regen it gets inversed: less turns in the rear (due slightly larger diameter) makes it look like the rear is slidding.  I think ICE bikes usually don't have deceleration (downsize) TC so the critieria for the computer programming is much easier.

Hope perfomance improves as the tire wears (although you  are right 2000 mi should have been enough)

[Specter]

i keep my TC set in the middle, and regen as high as it will go.  never really had issues with it unless i was on a really dirty road and i could feel it skidding a bit on the dirt.

ice bikes have engine braking but i don't think it's nearly as aggressive as regen can be, and you are correct, if it has to 'dump' regen a few times because of traction issues, it'll basically null it until you cycle power or severely neuter it.  yah that can get annoying but i have found out that in a wc scenario you can cycle power on a ribelle and she'll pick right back up and green light still going 80 mph.  just give it a bit of gas to try to match about where you think your speed is at for when it does 'catch' so it's not such an abrupt jump back to power.

turning it a bit less sensitive, and that should help with nuisance set offs.

Aaron

[Demoni]

I think our bikes are particularly sensitive because they have to control TC both when accelerating AND when decelerating (regen). It's all about the relative wheel rotation speed between rear and front...

^ Anav pretty much nailed it.

The TC system compares front and rear wheel speed values. Each TC setting will allow a certain delta between these values before reducing the requested motor power transmitted to the rear wheel. The lower the TC number the greater the allowed speed delta will be, resulting in less intervention. You can see this in action if you have your bike on a rear stand. With the TC set to 6 (highest) when you apply the throttle the rear wheel will only spin at ~5mph, changing the TC value to 1 will allow the rear wheel to turn much faster before the TC intervenes.

Tire manufactures do not all use the same profiles, some are more round where others are more egg shaped. As you lean the bike the part of the tire that is in contact with the road will get smaller, resulting is a taller final drive ratio (the bike will have a higher speed when leaned over for a given RPM). If front and rear tires have a similar profile they would change their ratios at the same rate. It sounds like in your case the difference between the front and rear profiles is higher than the wheel speed delta for the TC mode you selected. Reducing the TC mode 1 lower should reduce the intervention.

[Grauteufel]

[/quote] difference between the front and rear profiles[/quote]

This is why a someone at at recent track/training day got a lecture on mixing a cheap chinese worn out front with a brand new Diablo Rosso Corsa 4 rear

[Specter]

difference between the front and rear profiles[/quote]

This is why a someone at at recent track/training day got a lecture on mixing a cheap chinese worn out front with a brand new Diablo Rosso Corsa 4 rear
[/quote]

ouch, that's a face plant waiting to happen.  whats even worse is a lot of people look at the front and say oh it's got tread left it's good, ignoring the sides, which have the cords showing and a valley you can stick your finger in...

Aaron

[jotjotde]

Thanks all for your input!
I understand that the majority agrees that most probably an unusual profile of the Dunlop tires are responsible for the TC going wild and this sounds reasonable to me.

In parallel I contacted Dunlop here in Germany and got an unsatisfactory three-sentence answer. Dunlop claim they had not heard of something similar yet but rule out a production fault.

For me, I draw the conclusion that the Dunlop is not the right tire for me.
In my youth I had a very nice tennis rack made by Dunlop.

[TNCreator]

do you have the standard or GT version of the roadsmart4 ?
I have the standard ones and also have a problem with TC sometime being all over the place.
maybe the standard version is flexing too much and the gt version could be a solution.