gts dyno scorpion

We mentioned having a Kübler Speedwheel fitted in our last Long Termer report and told you what our first impressions were. Now we’ve had time to use the GTS for a couple of extra months we thought it was worth bringing you an update.

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What is it?

Just to recap, for those who may not know what this simple device is, it’s simply a replacement rear ABS ring. It costs around £50 for a genuine Kübler one (ours came from Scooter Center and was fitted by Ron Daley Scooters, who also supply them). The Speedwheel is calibrated properly, unlike the Piaggio ABS ring – which over reads quite considerably. The speed-controlled rev limiter kicks in earlier than it should on the standard GTS HPE as a result, meaning that although the HPE is the most powerful Vespa GTS ever produced, it’s also the slowest at the top end. In the world before GPS this would never have been known but the modern world means we can all measure ‘real world’ speeds, rather than relying on the actual speedo (in 17 years of road testing scooters for a living I’ve never seen an accurate speedo).

An older 250/300 Vespa GTS would achieve 82mph on GPS, the HPE can only manage 77. That means it’ll hit the limiter all the time at motorway speeds (let’s face it, who travels at 70mph?) and not leave you enough power for overtaking. This is the only downside to GTS 300 HPE ownership. Thankfully it is cheap and easy to resolve. Instantly you’ll notice a difference when you ride the GTS HPE on a fast road with a Speedwheel fitted.

Sometimes the simplest of things are the most effective...
Sometimes the simplest of things are the most effective…

Gaining extra MPH on a four-stroke scooter isn’t usually cheap or easy and gaining it on a GTS has always been difficult thanks to it’s hard to overcome rev limiter. Luckily the Speedwheel laughs in the face of electronics, by simply making it read the correct speed you gain 6.6mph and the scooter is much nicer to ride. Piaggio should be doing this at the factory, it’s hardly rocket science. The harsh rev limiter (it’s much nastier than on the previous GTS) spoils motorway riding.

Stubborn bolts

We mentioned last time that the standard ABS ring now comes with thread lock on the soft allen bolts, which means the bolts will round off when you try to remove them. Expect to have to use heat, decent tools and maybe even resort to cutting a slot in the bolts to remove them (although a Torx bit can also be used to get troublesome allen bolts out). You’ll need to replace the bolts though whatever you use.

Recalibration of the Vespa GTS ABS

When you fit a Speedwheel (or replace the tyres on an ABS/ASR equipped GTS) you’ll need to go through the recalibration procedure (if you have your HPE Vespa owner’s manual you can read the full details on pages 24-25.)

Here’s a quick run-through though…

  1. When you turn the ignition on the ABS & ASR warning lights will flash quickly to indicate a fault.
  2. Start the scooter and ride a short distance above 3mph and wait for the lights to stop flashing.
  3. Stop the scooter and leave it idling for at least three seconds.
  4. Turn the ASR system off by pressing the ASR button on the handlebars and check that the ASR icon remains steady.
  5. Press both the engine starter button and ASR button for at least 4 seconds.
  6. Once the procedure is activated the ASR icon will start to flash slowly (once every two seconds).
  7. Ride the scooter to a constant speed of 18.7mph (30kmh) for at least 10 seconds.
  8. Once the ASR light goes out the procedure is complete
  9. Once complete stop the scooter and turn the ignition off for at least 30 seconds.

It’s not quite as long-winded as it sounds but if you can’t maintain the constant speed in step 7 you’ll have to restart the procedure. Also, if you’ve not completed the recalibration within two minutes the ASR symbol will remain illuminated until the scooter is turned off again. To restart the ASR you’ll need to start from step 1 again.

VIDEO | On the Dyno with Speedwheel

Dyno results

Scorpion Exhausts kindly allowed us to put the HPE on their in-house dyno before and after the Speedwheel was fitted. On the dyno it’s quite obvious that the Speedwheel is doing its job. The red line shows the GTS as standard. Look along the bottom of the graph and you’ll see the power drops like a stone as the rev limiter hits at 77mph. Compare that to the blue line (Speedwheel fitted), although the power tails off it allows the scooter to get to 84mph. Max power is also slightly up to 20.6bhp at the rear wheel but we’ll ignore that, it’s more likely to do with the GTS having loosened up a bit more by the time it was tested with the Speedwheel.

Those speeds correspond perfectly with what the scooter feels like on the road and the speeds recorded by GPS.

Speedwheel dyno

Conclusion

Not only does the Speedwheel do exactly what it says on the tin but it also makes the digital speedo as accurate as it should be. For a four-stroke scooter you can’t buy better bolt-on tuning. If you do lots of motorway miles, or enjoy the top end of your Vespa GTS this will transform the only negative thing about the new HPE. All for just £50, buy one.

Disclaimer

Fitting a Speedwheel may well invalidate your warranty and will have a negative effect on your ABS. Whether it’s worth it or not is up to the individual.

SLUK makes and sells products to protect and style up your Vespa GTS – visit the SLUK Shop

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Buy genuine SLUK products!

SLUK invented the SLUK Guard, SLUK Catcher and SLUK Tail, as well as the SLUK Support (and numerous other items). All our SLUK Plastics™ are designed by Scooterists, for Scooterists, they’re hand made in England by our artisan craftsman, Nigel – rather than in some Chinese/Indian sweatshop and are used by us and our customers around the world.

Trust in SLUK.

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