Got it: "GTRO Gearbox" is an alternative to the Sturmey-Archer gearbox on the EVO

http://www.efneo.com/gearbox/

I'm confused.

Is the meters of development of the 18"-wheeled EVO 3,45 - 5,51m or 3,51 - 6,28m ?

[size=120][b]Strida efneo GTRO with 16" wheels[/b]
(tyre size 16 x 1,5)[/size]

[b]Gear inches[/b]:

in [b]low gear[/b]: 16" x 80 x 1 ÷ 30 = [b]42,7"[/b]

in [b]middle gear[/b]: 16" x 80 x 1,43 ÷ 30 = [b]61"[/b]

in [b]high gear[/b]: 16" x 80 x 1,79 ÷ 30 = [b]76,4"[/b]


[b]Metres of development[/b]:

in [b]low gear[/b]: 1,185m × 80 x 1 ÷ 30 = [b]3,16m[/b]

in [b]middle gear[/b]: 1,185m × 80 × 1,43 ÷ 30 = [b]4,52m[/b]

in [b]high gear[/b]: 1,185m × 80 × 1,79 ÷ 30 = [b]5,66m[/b]




[size=120][b]Strida efneo GTRO with 18" wheels[/b]
(tyre size 18 x 1,25)[/size]

[b]Gear inches[/b]:

in [b]low gear[/b]: 18" x 80 x 1 ÷ 30 x = [b]48"[/b]

in [b]middle gear[/b]: 18" x 80 x 1,43 ÷ 30 = [b]68,6"[/b]

in [b]high gear[/b]: 18" x 80 x 1,79 ÷ 30 = [b]85,9"[/b]


[b]Metres of development[/b]:

in [b]low gear[/b]: 1,315m × 80 x 1 ÷ 30 = [b]3,51m[/b]

in [b]middle gear[/b]: 1,315m × 80 × 1,43 ÷ 30 = [b]5,01m[/b]

in [b]high gear[/b]: 1,315m × 80 × 1,79 ÷ 30 = [b]6,28m[/b]

[i]Once more I have to apologize - for claiming that the gear ratios of the low and high EVO gear would be completely equal to them of the SD/MAS.
That's not correct - sorry[/i] :oops:

Principially can be said;
for [b]16" EVO[/b]:

The [b]low[/b] gear ratio is [u]similar[/u][b]*[/b] to the low gear ratio of the SD or MAS,
the [b]middle[/b] gear (direct drive) is [u]equal[/u] to LT or 5.xx,
and the [b]high[/b] gear is [u]similar[/u][b]*[/b] to the high gear of SD or MAS.

for [b]18" EVO[/b]:

The [b]low[/b] gear ratio is [u]similar[/u][b]*[/b] to the low gear ratio of the SD/MAS with 18" wheels,
the [b]middle[/b] gear (direct drive) is [u]equal[/u] to SX,
and the [b]high[/b] gear is [u]similar[/u][b]*[/b] to the high gear of SD or MAS with 18" wheels.

[b]*[/b]Expressed in numbers, regardless of wheel size:

The overall gear ratio of the EVO drive in 1st gear (2,623) is lower ( ~ 1,6 %)
than the low gear of the speed drive (2,666).

The overall gear ratio of the EVO drive in 3rd gear (4,19) is lower (~ 5 %)
than the high gear of the speed drive (4,4).

Using Amuro's calculated circumferences and the gear ratios of the EVO drive it is not that difficult to complete the post above:

[size=120][b]Strida EVO with 16" wheels[/b]
(tyre size 16 x 1,5)[/size]

[b]Gear inches[/b]:

in [b]low gear[/b]: 16" x 100 x 0,787 ÷ 30 = [b]42"[/b]

in [b]middle gear[/b]: 16" x 100 x 1 ÷ 30 = [b]53,3"[/b]

in [b]high gear[/b]: 16" x 100 x 1,257 ÷ 30 = [b]67"[/b]

[b]Metres of development[/b]

in [b]low gear[/b]: 1,185m × 100 x 0,787 ÷ 30 = [b]3,11m[/b]

in [b]middle gear[/b]: 1,185m × 100 × 1 ÷ 30 = [b]3,95m[/b]

in [b]high gear[/b]: 1,185m × 100 × 1,257 ÷ 30 = [b]4,97m[/b]



[size=120][b]Strida EVO with 18" wheels[/b]
(tyre size 18 x 1,25)[/size]

[b]Gear inches[/b]:

in [b]low gear[/b]: 18" x 100 x 0,787 ÷ 30 x = [b]47,2"[/b]

in [b]middle gear[/b]: 18" x 100 x 1 ÷ 30 = [b]60"[/b]

in [b]high gear[/b]: 18" x 100 x 1,257 ÷ 30 = [b]75,4"[/b]

[b]Metres of development[/b]

in [b]low gear[/b]: 1,315m × 100 x 0,787 ÷ 30 = [b]3,45m[/b]

in [b]middle gear[/b]: 1,315m × 100 × 1 ÷ 30 = [b]4,38m[/b]

in [b]high gear[/b]: 1,315m × 100 × 1,257 ÷ 30 = [b]5,51m[/b]

Thanks for the useful information. Yesterday I was calculating the rim diameter in mm (kojak Schwalbe 18x1.25) and the result was 1315 mm, which checked with the data seen here =)

Just a quick message to mention this excellent calculator dedicated to the single speed:

http://software.bareknucklebrigade.com/rabbit.applet.html

[quote="marcio123"]
Limitation on SX is gear ratio - not power let's be real.
When I go 30km/h on sx I have to move my legs creazy fast.
[/quote]

Yes ,but the MAS has still a higher gear ratio, and at the same pedaling frequency you come into a speed range where the aerodynamics get more important. Because the frontal area on a Strida is really bad:
[img]http://lh3.ggpht.com/_ZbDra3wdwgo/SR6hG92drVI/AAAAAAAABto/K5NlTeUBBoo/Tall%20Guy%20on%20Strida.jpg[/img]

I personally can't sustain the same pedaling frequency in high gear as with my LT 16".

If you like speed, buy a recumbent instead :wink:
[img]http://rekuvalromaba.evobike.hu/wp-content/uploads/2010/08/recumbent.jpg[/img]
[img]http://www.meta-bikes.com/images/turbulence455.jpg[/img]

Come on guys ;)
Limitation on SX is gear ratio - not power ;) let's be real.
When I go 30km/h on sx I have to move my legs creazy fast.

Is there anybody who was both SX and MAS ? Can You test this gear ratio ?

Well said, thank you Bietrume!

[img]http://www.peppiclip.de/Smilies/assets/images/cool10.GIF[/img]

The speed increases you mention are theoretical: don't forget that rolling resistance increases linearly with the speed and air resistance increases quadratically with the speed.

So depending on your physical condition, it might be that the limiting factor will be your maximum power rather than your maximum pedaling frequency.

So Strida MAS (16") is 18% faster than SX.
On my SX I can make up to 30km/h while in spec there is 24km/h

Strida MAS has 25 km/h in spec but maybe there should be 24 km/h +18% which is 28 km/h.

I can make 30 km/h on SX (24 in spec) so I should reach about 35 km/h on MAS which is really reasonable speed.

Has anybody tried it in real life ? How much faster is MAS than SX ?

[b]Comparison among the [url=http://en.wikipedia.org/wiki/Gear_inches]gear inches[/url], [url=http://en.wikipedia.org/wiki/Gear_inches#Calculating_metres_of_development]metres of developments[/url] and [url=http://www.sheldonbrown.com/gain.html]gain ratios[/url] of different models of Strida[/b]

Information about measuring gears:
[url]http://en.wikipedia.org/wiki/Bicycle_gearing#Measuring_gears[/url]


[size=120][b]Strida 1[/b], [b]Strida 2[/b], [b]Strida 3[/b], [b]Strida 5[/b] and [b]Strida LT[/b][/size]

[b]Gear inches[/b]: 16" × 100 ÷ 30 = [b]53.3"[/b]

[b]Metres of development[/b]: 1.185m × 100 ÷ 30 = [b]3.95m[/b]
This means that the bike travels about 3.95 metres per crank rotation.

[b]Gain ratio[/b]: 1185mm ÷ π ÷ 2 ÷ 170mm × 100 ÷ 30 = [b]3.70[/b]


[size=120][b]Strida Mini[/b][/size]

[b]Gear inches[/b]: 14" x 88 ÷ 30 = [b]41"[/b]

[b]Metres of development[/b]: 1.02m × 88 ÷ 30 = [b]2.99m[/b]
This means that the bike travels about 2.99 metres per crank rotation.

[b]Gain ratio[/b]: 1020mm ÷ π ÷ 2 ÷ 150mm × 88 ÷ 30 = [b]3.17[/b]
This reflects the reason why Strida mini has lower value on both gear inches and metres of development than Strida SD in low gear but you still feel pedalling harder on a Strida mini than on a Strida SD in low gear when going up an incline. It is because the crank arms used on Strida Mini (150mm) is shorter than those used on Strida SD and other models of Strida (170mm).


[size=120][b]Strida SX[/b][/size]

[b]Gear inches[/b]: 18" × 100 ÷ 30 = [b]60"[/b]

[b]Metres of development[/b]

with [b]Innova tyres[/b]: 1.325m × 100 ÷ 30 = [b]4.42m[/b]
This means that the bike travels about 4.42 metres per crank rotation.

with [b]Schwalbe Kojak tyres[/b]: 1.315m × 100 ÷ 30 = [b]4.38m[/b]
This means that the bike travels about 4.38 metres per crank rotation.

[b]Gain ratio[/b]

with [b]Innova tyres[/b]: 1325mm ÷ π ÷ 2 ÷ 170mm × 100 ÷ 30 = [b]4.13[/b]

with [b]Schwalbe Kojak tyres[/b]: 1315mm ÷ π ÷ 2 ÷ 170mm × 100 ÷ 30 = [b]4.10[/b]


[size=120][b]Strida SD[/b] and the [b]MAS Special Edition[/b][/size]

[b]Gear inches[/b]

in [b]low gear[/b]: 16" x 80 ÷ 30 = [b]42.7"[/b]

in [b]high gear[/b]: 16" x 80 x 1.65 ÷ 30 = [b]70.4"[/b]

[b]Metres of development[/b]

in [b]low gear[/b]: 1.185m × 80 ÷ 30 = [b]3.16m[/b]
This means that the bike travels about 3.16 metres per crank rotation in low gear.

in [b]high gear[/b]: 1.185m × 80 × 1.65 ÷ 30 = [b]5.21m[/b]
This means that the bike travels about 5.21 metres per crank rotation in high gear.

[b]Gain ratio[/b]

in [b]low gear[/b]: 1185mm ÷ π ÷ 2 ÷ 170mm × 80 ÷ 30 = [b]2.96[/b]

in [b]high gear[/b]: 1185mm ÷ π ÷ 2 ÷ 170mm × 80 x 1.65 ÷ 30 = [b]4.88[/b]


[size=120][b]Strida equipped with speed-drive and 18" wheels[/b]
(with Schwalbe Kojak tyres)[/size]

[b]Gear inches[/b]:

in [b]low gear[/b]: 18" x 80 ÷ 30 = [b]48"[/b]

in [b]high gear[/b]: 18" x 80 x 1.65 ÷ 30 = [b]79.2"[/b]

[b]Metres of development[/b]

in [b]low gear[/b]: 1.315m × 80 ÷ 30 = [b]3.51m[/b]
This means that the bike travels about 3.51 metres per crank rotation in low gear.

in [b]high gear[/b]: 1.315m × 80 × 1.65 ÷ 30 = [b]5.79m[/b]
This means that the bike travels about 5.79 metres per crank rotation in high gear.

[b]Gain ratio[/b]

in [b]low gear[/b]: 1315mm ÷ π ÷ 2 ÷ 170mm × 80 ÷ 30 = [b]3.28[/b]

in [b]high gear[/b]: 1315mm ÷ π ÷ 2 ÷ 170mm × 80 x 1.65 ÷ 30 = [b]5.42[/b]

[quote="Amuro Lee"]For a more precise calculation, the size of the tyres used on 16" wheeled Stridas is 16 x 1.50 or 40-305 in Therefore, the actual gear ratio of Strida 1, Strida 2, Strida 3, Strida 5 and Strida LT is 14.85" × 100 ÷ 30 [b]= 49.5 gear inches.[/b][/quote]
That is about right I think. I noticed that my Strida copy has a lower ratio than the mid ratio in my Merc which I have calculated to be 60". This puzzled me a bit because of the claims on various websites that the Strida ratio is 56". I was sure it felt lower myself since I ride both bikes.

I measured the circumference of my wheel with 16x1.75 tyres at 1220. I made the measurement three times by doing a roll out and got an identical figure. I make my ratio at a shade under 51" (50.956). Exact ratio depends on tyres like you say. It is way lower than 56" though.

For a more precise calculation, the size of the tyres used on 16" wheeled Stridas is 16 x 1.50 or 40-305 in [url=http://www.schwalbetires.com/tech_info/size_markings]ETRTO[/url] system.
According to the tyre circumference cross reference table on the [url=http://www.cateye.com/sites/cateye/upload/manuals/en/MC100Wv2ENG.pdf]instruction manual[/url] of my cyclocomputer, the actual circumference of a 16 x 1.50 (40-305) sized tyre should be 1185mm. Then, the actual diameter should be 1185 ÷ 25.4 ÷ π = 14.85".
Therefore, [b]the actual gear ratio of Strida 1, Strida 2, Strida 3, Strida 5 and Strida LT is[/b] 14.85" × 100 ÷ 30 = [b]49.5 gear inches[/b].

In the case of Strida Mini, the size of the tyres is 14 x 1.50 or 40-254 in ETRTO system. The circumference of the tyres is 1020mm. Then, the actual diameter is 1020 ÷ 25.4 ÷ π = 12.78". Therefore, [b]the actual gear ratio of Strida Mini should be[/b] 12.78" × 88 ÷ 30 = [b]37.5 gear inches[/b].

However, Strida Mini uses shorter crank arms compared with a normal sized Strida with 170mm crank length so the gear ratio feeled by the rider will be higher than the actual gear ratio. :?

On [b]Strida SX with [url=http://hk.myblog.yahoo.com/STRIDA-HK/article?mid=189]Innova tyres[/url][/b], the size of the tyres is 18 x 1.35 or 35-355 in ETRTO system. The circumference of the tyres is 1325mm. Then, the actual diameter is 1325 ÷ 25.4 ÷ π = 16.6". Therefore, [b]the actual gear ratio should be[/b] 16.6" × 100 ÷ 30 = [b]55.3 gear inches[/b].

On [b]Strida SX with Schwalbe Kojak tyres[/b], the size of the tyres is 18 x 1.25 or 32-355 in ETRTO system. The circumference of the tyres is 1315mm. Then, the actual diameter is 1315 ÷ 25.4 ÷ π = 16.48". Therefore, [b]the actual gear ratio should be[/b] 16.48" × 100 ÷ 30 = [b]54.9 gear inches[/b].

On [b]Strida SD[/b] and the [b]MAS Special Edition[/b], [b]the actual gear ratio in low gear is[/b] 14.85" x 80 ÷ 30 = [b]39.6 gear inches[/b] and [b]the actual gear ratio in high gear is[/b] 14.85" x 80 x 1.65 ÷ 30 = [b]65.3 gear inches[/b].

On [b]Strida equipped with speed-drive and 18" wheels[/b] (with Schwalbe Kojak tyres), [b]the actual gear ratio in low gear is[/b] 16.48" x 80 ÷ 30 = [b]43.9 gear inches[/b] and [b]the actual gear ratio in high gear is[/b] 16.48" x 80 x 1.65 ÷ 30 = [b]72.5 gear inches[/b].