Extralite UltraBottom 51-52

Extralite UltraBottom 51-52 integrated lower half headset for 1.1/8"-1.1/2" tapered forks. With high quality angular contact bidirectional stainless bearing. Only 25.3 gr weight. Compatibie with 51/52 mm lower head tube bore frames. Made in Italy.


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Extralite UltraBottom 51-52 are a member of UltraTopBottom headsets big family, developed by Extralite to fit almost every different headset standard on the market.

extralite ultrabottom 51-52

All these different standards makes confusion and isn't so easy to know which standard is correct for yur bike, so the best way to go is to measure frame headtube bore with the help of a precision caliper :

extralite ultrabottom 51-52

With the correct measure and the help of the follow chart, you should be able to choose the correct headset for your bike. You can also find an high-resolution version of this chart inside product pictures.

extralite ultrabottom 51-52

Extralite UltraBottom 51-52 is the lower part of an integrated headset that will fit frames with integrated tapered (1.1/8"-1.1/2") headset. Lower headtube bore must have 51 or 52 mm inner diameter. Correct fitting is allowed by the tapered head of the headset bearing.

Headset Equipment :

  • An high quality bidirectional stainless steel bearing with double seals
  • A superlight Al 7075T6 CNC lower cone, easy to install and remove without tools
  • A taperhead bottom spacer


The weight in only 25.3 gr. (27 gr. optional spacer included) so a great value for a product that it's also better in quality than stock cheap headsets.

extralite ultrabottom 51-52

Stainless steel avoid corrosion, and the high quality bearing will assure a precise and smooth action and also a longer life.

Extralite Headsets has a minor stack height than standard ones especially for the upper part of the headset. This is an advantage because  :

  • You can get a lower handlebar riding height with the same steering/control parts, and this is important especially with 29" bicycles.
  • You can use a fork that has a short cutted headtube.
  • You can use a fork with a longer travel without modify handlebar riding height (of course steering angle will change a little)


We remember you that's also possible to use standard 1.1/8" forks on frames with tapered headset, with the help of the special  Extralite Extrabolt 16 adapter :

extralite ultrabottom 51-52

With this adapter headset bearing will work directly on and headset tapered lower cone will not be installed.

Extralite UltraBottom 51-52 is an high quality product Made in Italy


Data sheet

Weight :
25.3 gr.
Headset Style :
Integrated Bottom
Head Tube Bore :
51 - 52 mm
Tolerance :
51.00 - 52.50 mm
Fork Standard :
Tapered 1.1/8" - 1.1/2"
IS51/40 o IS52/40
Stack Height :
1 mm
Bearing Type :
Bidirectional cartridge
Bearing Material :
Stainless Steel
Use :
MTB, Road
Fitting :
Specialized Stumjumper HT Carbon, Epic Carbon, etc.
Range of use :
Max rider weight :


Ultrabottom 51-52 User Manual

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