NX250 fork spring mods

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scrambler
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Beiträge: 4347
Registriert: Fr Sep 14, 2012 8:50 am

NX250 fork spring mods

Beitrag von scrambler » Sa Jan 04, 2020 7:50 am

Unlike the rear shock, the front fork isn’t too bad – at least with an rider of average weight. The main downsize is too much negative suspension travel (or "sag") with the side effect that the NX is pretty unstable on the kickstand and easily tips over. The sag is measured with the rider sittting on the bike – in my case with a stock fork its 7cm or 34% of the total way of travel. Too much – usually something between 20 and 30 % is recommended.

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So I tried a couple of aftermarket fork springs. Remarkable: none of them have the same length as the stock springs. It looks like that, even though the manufactors claim that the springs were specifically made for the NX250, they were taken from some other bike.
Negative consequences: the aftermarket springs are either too long or too short, so you have to either made some spacers or use massive force to screw in the fork plugs.

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No wonder that almost all of the (expensive) aftermarket springs are not really much of an improvement – White Power and Promoto are still too soft and Wirths are way too hard. Maybe the Wirths work better with a riders weight of more than 100kg – but I haven’t tried that.
The best of the bunch i.m.o are the Hyperpro https://www.ebay.de/itm/KIT-MOLLE-FORCE ... SwPAlcnOBU, but they are also the most expensive. They work pretty well even at higher off-road speed. The hyperpros came with 25 grade fork oil, the others with 15 oil, if I remember correctly.

Since I was pretty disappointed with the aftermarket parts I was looking for an affordable alternative and stumbled over these adjustable fork plugs https://www.ebay.de/itm/1-Pair-37mm-CNC ... Swj61cg3c7 . With those the sag can be adjusted between 19 and 29%. It works even (with 15 grade fork oil) better when the short top springs are replaced with 8.5cm (~ 3.5'') long spacers.

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jonathan
Beiträge: 36
Registriert: Fr Sep 13, 2019 12:11 am

Re: NX250 fork spring mods

Beitrag von jonathan » Do Jan 23, 2020 12:01 am

I fitted a pair of preload adjusters to my AX1 but haven't set anything up yet as the bike is still in bits. Only had a relatively short ride (50Km) on the road after buying the bike, before I decided to strip it down, but in that short time I figured the front end was soft, but really compliant. The previous owner had fitted a hagon shock and the preload was way too much, so the bike felt like it was pitched forward....in his defense, he said he'd only just installed it and hadn't played around with the settings.

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