SRAM dual drive experience

[rsyme]

Has anyone got experience of the 27 gear SRAM dual drive as on Haibike's xDuro trekking? Is this amount of gears required? Are they usable in real day to day riding? Or are they just a marketing gimmick?

Are there any independent test write-ups available?

Robbie

 

[Martin@e-bikeshop]

Think about it, on a normal bike, say 24 speed. You only have about 14 usable gears, as you cant use gear 1 with gear 3 on the front or gear 1 with gear 3 on the back etc. You cant cross over.

The beauty of the DD is that you actually have 27 'usable' gears! Its one of the only Bosch eBikes to do so. Great for long distance trekking or hilly areas with a full range of gears.

My full write up here.

Reviews here. (Click on the reviews tab)

Or full article review of eBike here.

Hope this helps!
Martin

 

[D C]

Just being a bit silly for a moment, if you added three rings at the front (on a bike which you could do this) would that give you 81 gears?

Dave.

 

[Blew it]

Has anyone got experience of the 27 gear SRAM dual drive as on Haibike's xDuro trekking? Is this amount of gears required?

In answer to your first question, twenty-seven gears are not needed on any electrically assisted bicycle. Nevertheless the SRAM DUAL-DRIVE is very useful in other ways. There are always occasions when we have to stop the bike quickly, then struggle to get going again in too high a gear. The Dual-drive can simply drop into under-drive whilst stationary allowing an easy getaway from an emergency stop. As I live in a moderately hilly area, I have never needed the under-drive ratios for hill climbing.

The over-drive ratios are very useful in two ways. On occasions where a stiff following wind is present, shifting up to overdrive allow a high speed to be maintained at a comfortable cadence. The longest gear available being around 127 gear-inches (of the top of my head). The over-drive ratios are also useful in reducing wear on the 11 Tooth sprocket. As with under-drive, the over-drive is indirect, therefore less efficient than the direct-drive middle range. I quite often ride continuously in over-drive, keeping the chain well away from the 11T cog. Yes, I can feel the slight drag associated with the indirect drive, but this is easily offset by the available electrical assistance.

My own Haibike eQ Trekking is over three years old now. Apart from the usual problems associated with the classic drive, the machine has proved thoroughly reliable and an absolute joy to ride.

Perhaps I should add, I am not a MAMIL, I am very easy to please.

 

[EddiePJ]

Robbie, despite the issues that I had with mine, the system is a very good one, and I certainly wouldn't say that it's a marketing gimmick.
For mechanical sympathy and good riding practice on any bike, it is wise to try to select the correct gear ratio prior to say climbing a hill. I found that for the smoothest gear selection to be made, you have almost have to falter between the change, and release the tension.
I also like the fact that cable stretch and any minor adjustments can be made in seconds whilst still on the move at the handle bar end.
The one aspect that I don't like, is that you need a spanner to remove the rear wheel. The nuts on my example were of exceptionally very poor quality, and were quickly replaced with higher spec ones.

 

[grldtnr]

Just being a bit silly for a moment, if you added three rings at the front (on a bike which you could do this) would that give you 81 gears?

Dave.

y
Yup has been done, seen a recumbent trike Set up like that, myself I don' t see the need for 81 gears!
G

 

[flecc]

Just being a bit silly for a moment, if you added three rings at the front (on a bike which you could do this) would that give you 81 gears?

Dave.

One Dual-Drive version uses a 10 sprocket cassette, so with a triple chainring a total of 90 gears.

I like the DualDrive, but see it as best suited to recumbents and especially recumbent trikes, since they are notoriously slower climbers yet are capable of very high speeds on the flat and downhill due to the superior aerodynamics. Therefore they have a very real need for an extremely wide gear range. Also a triple chainring can be more of a problem between the legs on a recumbent since the chainline can closely follow the legs for some distance back

On a normal bike I think the usual triple chainring and rear cassette only is somewhat better if with skilled gears usage to maintain a straight chainline.

And as Blew it posted, 27 or more gears are not needed on an e-bike.
.

 

[Aushiker]

Think about it, on a normal bike, say 24 speed. You only have about 14 usable gears, as you cant use gear 1 with gear 3 on the front or gear 1 with gear 3 on the back etc. You cant cross over.

That is really not 100% correct ... you can cross over ... all six of my bikes can easily cross-chain. On the other hand, the more appropriate question is it a smart thing to do ... some say no, some say with modern chains it is not a big issue.

Personally whilst I don't generally do it, I have done and the sky hasn't fallen in.

Andrew

 

[flecc]

That is really not 100% correct ... you can cross over ... all six of my bikes can easily cross-chain. On the other hand, the more appropriate question is it a smart thing to do ... some say no, some say with modern chains it is not a big issue.

Personally whilst I don't generally do it, I have done and the sky hasn't fallen in.

Andrew

I agree Andrew, and I've also had bikes easily capable of that. In fact there is very little loss of efficency from running a chain out of line, certainly not enough to be of concern.

However, there is a loss of useful gear numbers with multiple sprocket/chainwheel derailleurs simply due to overlap, pairs having ratios almost exactly coinciding with other pairings.

Here's an example from a setup on a previous normal bike with a triple chainring and 7 sprocket cassette, these were the exact duplicates and close pairings or triplings in gear inches:

33/34, 40/40, 46/45/46, 55/53/54.

So those ten gears were only four in effect, reducing the nominal 21 gears to only 15 actually distinct ratios. Similar is true of any multi-chainring derailleur setup, the more nominal ratios, the greater the number of overlaps.
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