BEC,
There are several factors to make a gravel capable e-bike of Vado SL. I assume your model is EQ, so you need to stick with 38 mm max diameter tires. Nothing wrong with that! My gravel-cycling buddies all ride on 700x38c tires, the prefered model being Schwalbe G-One Allround. The problem here is Schwalbe believes 38c is 40 mm while Specialized are firm on 38c = 38 mm! With tight fender clearance, I would not risk putting 40 mm tires on Vado SL EQ. The next and very safe size is 35-622. Now, my experience:
I chose Schwalbe Smart Sam 37-622 for warm season gravel rides. The tire is strong, silent on pavement, very good grip in more rough terrain. For winter, I use Schwalbe Marathon Winter Plus 35-622, with the extra benefit of increased fender clearance (easy removing snow/mud, and not getting clogged).
However, it is not only the tire size! For instance, you could inflate your tires closer to the allowed minimum, especially if you are not a heavy person. Makes miracles.
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The handlebar position. Hard question. You might feel bad with the bars very low but almost all gravel cyclists all ride drop bars (only some use flat bars as we do for Vado SL). I actually lowered my Vado SL handlebars to the minimum and feel better on my rides! You could also try SQlab Innerbarends 411 (handlebar "hoods"). With the low handlebar position, riding in the Innerbarends as if they were hoods of the road bike drop bars is a very interesting and beneficial experience. Your arms are closer apart, more of your body weight rests on these "hoods", the ride is less shaky, and there's excellent reach to both brake levers and the shifter (I am a convert now!)
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One of versions of Redshift ShockStop is the 30 deg one. If you want to "gravelize" your Vado SL, don't get tempted with that version! The proper variety would be the +/- 6 deg, and the stem length could be either 100 or 120 mm depending on the reach of your arms. Now, hear what the Redshift ShockStop can do for you:
I used to own a premium full suspension Giant e-MTB. It has a long travel air-fork and 2.6" lowly inflated tires. The ride comfort with Redshift Shock Stop stem can be compared to that suspension system but it gives a better ride experience than the Fox fork! It is because the MTB fork is for maintaining traction with rough terrain but it is not meant for increased ride comfort (it is the 2.6" tyres that do it!) It happened to me to inadvertently
lock out the suspension in the Giant and be bombing downhill on rocks! And I hardly felt any difference!
Now, the Redshift ShockStop stem. It is a painkiller. When you ride on any rough surface, such as cracked asphalt, gravel, or on easy off-road trail, you actually
know the terrain is rough but you
do not suffer at all! The ride impression is as if the frame of your Vado SL were breaking, as the e-bike feels very elastic. But it is so fantastic as you do not suffer from the imperfect surfaces at all!
The issue to install the RockStop stem is you need to relocate the headlight. I have used a good GoPro mount made of strong aluminium alloy, and the benefit is the lamp is more forward, extending past the cables.
BEC, I'm telling you: RedShift ShockStop stem was the best investment I have ever done to my Vado SL! I have been on gravel cycling rides with my buddies. The leader commented: "I need to say Stefan was eating kilometres like a youngster!"